No. 1

  Measurement of Physical Quantities

    Pages

Zuzana Rošťáková, Roman Rosipal: 

Time Alignment as a Necessary Step in the Analysis of Sleep Probabilistic Curves

Abstract: 

Sleep can be characterised as a dynamic process that has a finite set of sleep stages during the night. The standard Rechtschaffen and Kales sleep model produces discrete representation of sleep and does not take into account its dynamic structure. In contrast, the continuous sleep representation provided by the probabilistic sleep model accounts for the dynamics of the sleep process. However, analysis of the sleep probabilistic curves is problematic when time misalignment is present. In this study, we highlight the necessity of curve synchronization before further analysis. Original and in time aligned sleep probabilistic curves were transformed into a finite dimensional vector space, and their ability to predict subjects’ age or daily measures is evaluated. We conclude that curve alignment significantly improves the prediction of the daily measures, especially in the case of the S2-related sleep states or slow wave sleep.

Grzegorz Tytko, Leszek Dziczkowski:

I-cored Coil Probe Located Above a Conductive Plate with a Surface Hole

Abstract: 

This work presents an axially symmetric mathematical model of an I-cored coil placed over a two-layered conductive material with a cylindrical surface hole. The problem was divided into regions for which the magnetic vector potential of a filamentary coil was established applying the truncated region eigenfunction expansion method. Then the final formula was developed to calculate impedance changes for a cylindrical coil with reference to both the air and to a material with no hole. The influence of a surface flaw in the conductive material on the components of coil impedance was examined. Calculations were made in Matlab for a hole with various radii and the results thereof were verified with the finite element method in COMSOL Multiphysics package. Very good consistency was achieved in all cases.

Zhaoyao Shi, Huixu Song, Hongfang Chen, Yanqiang Sun:

Research on Measurement Accuracy of Laser Tracking System Based on Spherical Mirror with Rotation Errors of Gimbal Mount Axes

Abstract: 

This paper presents a novel experimental approach for confirming that spherical mirror of a laser tracking system can reduce the influences of rotation errors of gimbal mount axes on the measurement accuracy. By simplifying the optical system model of laser tracking system based on spherical mirror, we can easily extract the laser ranging measurement error caused by rotation errors of gimbal mount axes with the positions of spherical mirror, biconvex lens, cat’s eye reflector, and measuring beam. The motions of polarization beam splitter and biconvex lens along the optical axis and vertical direction of optical axis are driven by error motions of gimbal mount axes. In order to simplify the experimental process, the motion of biconvex lens is substituted by the motion of spherical mirror according to the principle of relative motion. The laser ranging measurement error caused by the rotation errors of gimbal mount axes could be recorded in the readings of laser interferometer. The experimental results showed that the laser ranging measurement error caused by rotation errors was less than 0.1 μm if radial error motion and axial error motion were within ±10 μm. The experimental method simplified the experimental procedure and the spherical mirror could reduce the influences of rotation errors of gimbal mount axes on the measurement accuracy of the laser tracking system.

Lenka Cepova, Andrea Kovacikova, Robert Cep, Pavel Klaput, Ondrej Mizera:

Measurement System Analyses – Gauge Repeatability and Reproducibility Methods

Abstract: 

The submitted article focuses on a detailed explanation of the average and range method (Automotive Industry Action Group, Measurement System Analysis approach) and of the honest Gauge Repeatability and Reproducibility method (Evaluating the Measurement Process approach). The measured data (thickness of plastic parts) were evaluated by both methods and their results were compared on the basis of numerical evaluation. Both methods were additionally compared and their advantages and disadvantages were discussed. One difference between both methods is the calculation of variation components. The AIAG method calculates the variation components based on standard deviation (then a sum of variation components does not give 100 %) and the honest GRR study calculates the variation components based on variance, where the sum of all variation components (part to part variation, EV & AV) gives the total variation of 100 %. Acceptance of both methods among the professional society, future use, and acceptance by manufacturing industry were also discussed. Nowadays, the AIAG is the leading method in the industry.

J. Sam Alaric, V. Suresh, A. Abudhahir, M. Carmel Sobia, M. Baarkavi:

Theoretical Analysis of the Rectangular Defect Orientation using Magnetic Flux Leakage

Abstract: 

This paper presents an approach to estimate the orientation of the rectangular defect in the ferromagnetic specimen using the magnetic flux leakage technique. Three components of the magnetic flux leakage profile, such as radial, axial, and tangential component are considered to estimate the orientation of the rectangular defect. The orientation of the rectangular defect is estimated by the proposed analytical model using MATLAB software. The results calculated by the analytical model are validated by the three-dimensional finite element analysis using COMSOL Multiphysics software. Tangential component provides better performance to estimate the orientation of the rectangular defect compared with radial and axial component of the magnetic flux leakage profile.

Tereza Komarkova, Pavel Fiala, Miloslav Steinbauer, Zdenek Roubal: 

Testing an Impedance Non-destructive Method to Evaluate Steel-Fiber Concrete Samples

Abstract: 

Steel-fiber reinforced concrete is a composite material characterized by outstanding tensile properties and resistance to the development of cracks. The concrete, however, exhibits such characteristics only on the condition that the steel fibers in the final, hardened composite have been distributed evenly. The current methods to evaluate the distribution and concentration of a fiber composite are either destructive or exhibit a limited capability of evaluating the concentration and orientation of the fibers. In this context, the paper discusses tests related to the evaluation of the density and orientation of fibers in a composite material. Compared to the approaches used to date, the proposed technique is based on the evaluation of the electrical impedance Z in the band close to the resonance of the sensor–sample configuration. Using analytically expressed equations, we can evaluate the monitored part of the composite and its density at various depths of the tested sample. The method employs test blocks of composites, utilizing the resonance of the measuring device and the measured sample set; the desired state occurs within the interval of between f=3 kHz and 400 kHz.

Top ↑

Measurement of Physical Quantities

Dragan Živanović, Milan Simić, Zivko Kokolanski, Dragan Denić, Vladimir Dimcev:

Generation of Long-time Complex Signals for Testing the Instruments for Detection of Voltage Quality Disturbances

Abstract: 

Software supported procedure for generation of long-time complex test sentences, suitable for testing the instruments for detection of standard voltage quality (VQ) disturbances is presented in this paper. This solution for test signal generation includes significant improvements of computer-based signal generator presented and described in the previously published paper [1]. The generator is based on virtual instrumentation software for defining the basic signal parameters, data acquisition card NI 6343, and power amplifier for amplification of output voltage level to the nominal RMS voltage value of 230 V. Definition of basic signal parameters in LabVIEW application software is supported using Script files, which allows simple repetition of specific test signals and combination of more different test sequences in the complex composite test waveform. The basic advantage of this generator compared to the similar solutions for signal generation is the possibility for long-time test sequence generation according to predefined complex test scenarios, including various combinations of VQ disturbances defined in accordance with the European standard EN50160. Experimental verification of the presented signal generator capability is performed by testing the commercial power quality analyzer Fluke 435 Series II. In this paper are shown some characteristic complex test signals with various disturbances and logged data obtained from the tested power quality analyzer.

Jingliang Chen, Jun Su, Orest Kochan, Mariana Levkiv:

Metrological Software Test for Simulating the Method of Determining the Thermocouple Error in Situ During Operation

Abstract: 

The simplified metrological software test (MST) for modeling the method of determining the thermocouple (TC) error in situ during operation is considered in the paper. The interaction between the proposed MST and a temperature measuring system is also reflected in order to study the error of determining the TC error in situ during operation. The modelling studies of the random error influence of the temperature measuring system, as well as interference magnitude (both the common and normal mode noises) on the error of determining the TC error in situ during operation using the proposed MST, have been carried out. The noise and  interference  of  the  order  of 5-6 μV cause the error of about 0.2-0.3°C. It is shown that high noise immunity is essential for accurate temperature measurements using TCs.

M. Dhamodaran, S. Jegadeesan, R. Praveen Kumar:

Analysis and Calculation of the Fluid Flow and the Temperature Field by Finite Element Modeling

Abstract: 

This paper presents a fundamental and accurate approach to study numerical analysis of fluid flow and heat transfer inside a channel. In this study, the Finite Element Method is used to analyze the channel, which is divided into small subsections. The small subsections are discretized using higher number of domain elements and the corresponding number of nodes. MATLAB codes are developed to be used in the analysis. Simulation results showed that the analyses of fluid flow and temperature are influenced significantly by the changing entrance velocity. Also, there is an apparent effect on the temperature fields due to the presence of an energy source in the middle of the domain. In this paper, the characteristics of flow analysis and heat analysis in a channel have been investigated.

Zhenyun Duan, Ning Wang, Jingshun Fu, Wenhui Zhao, Boqiang Duan, Jungui Zhao:

High Precision Edge Detection Algorithm for Mechanical Parts

Abstract: 

High precision and high efficiency measurement is becoming an imperative requirement for a lot of mechanical parts. So in this study, a subpixel-level edge detection algorithm based on the Gaussian integral model is proposed. For this purpose, the step edge normal section line Gaussian integral model of the backlight image is constructed, combined with the point spread function and the single step model. Then gray value of discrete points on the normal section line of pixel edge is calculated by surface interpolation, and the coordinate as well as gray information affected by noise is fitted in accordance with the Gaussian integral model. Therefore, a precise location of a subpixel edge was determined by searching the mean point. Finally, a gear tooth was measured by M&M3525 gear measurement center to verify the proposed algorithm. The theoretical analysis and experimental results show that the local edge fluctuation is reduced effectively by the proposed method in comparison with the existing subpixel edge detection algorithms. The subpixel edge location accuracy and computation speed are improved. And the maximum error of gear tooth profile total deviation is 1.9 μm compared with measurement result with gear measurement center. It indicates that the method has high reliability to meet the requirement of high precision measurement.

Jacek Bartman, Bogdan Kwiatkowski:

The Influence of Measurement Methodology on the Accuracy of Electrical Waveform Distortion Analysis

Abstract: 

The present paper covers a review of documents that specify measurement methods of voltage waveform distortion. It also presents measurement stages of waveform components that are uncommon in the classic fundamentals of electrotechnics and signal theory, including the creation process of groups and subgroups of harmonics and interharmonics. Moreover, the paper discusses selected distortion factors of periodic waveforms and presents analyses that compare the values of these distortion indices. The measurements were carried out in the cycle per cycle mode and the measurement methodology that was used complies with the IEC 61000-4-7 norm. The studies showed significant discrepancies between the values of analyzed parameters.

  Measurement in Biomedicine

Jean-Marc Luukinen, Daniel Aalto, Jarmo Malinen, Naoko Niikuni, Jani Saunavaara, Päivi Jääsaari, Antti Ojalammi, Riitta Parkkola, Tero Soukka, Risto-Pekka Happonen:

A Novel Marker Based Method to Teeth Alignment in MRI

Abstract: 

Magnetic resonance imaging (MRI) can precisely capture the anatomy of the vocal tract. However, the crowns of teeth are not visible in standard MRI scans. In this study, a marker-based teeth alignment method is presented and evaluated. Ten patients undergoing orthognathic surgery were enrolled. Supraglottal airways were imaged preoperatively using structural MRI. MRI visible markers were developed, and they were attached to maxillary teeth and corresponding locations on the dental casts. Repeated measurements of intermarker distances in MRI and in a replica model was compared using linear regression analysis. Dental cast MRI and corresponding caliper measurements did not differ significantly. In contrast, the marker locations in vivo differed somewhat from the dental cast measurements likely due to marker placement inaccuracies. The markers were clearly visible in MRI and allowed for dental models to be aligned to head and neck MRI scans.

Top ↑

Measurement of Physical Quantities

Morteza Daneshmand, Egils Avots, Gholamreza Anbarjafari:

Proportional Error Back-Propagation (PEB): Real-Time Automatic Loop Closure Correction for Maintaining Global Consistency in 3D Reconstruction with Minimal Computational Cost

Abstract: 

This paper introduces a robust, real-time loop closure correction technique for achieving global consistency in 3D reconstruction, whose underlying notion is to back-propagate the cumulative transformation error appearing while merging the pairs of consecutive frames in a sequence of shots taken by an RGB-D or depth camera. The proposed algorithm assumes that the starting frame and the last frame of the sequence roughly overlap. In order to verify the robustness and reliability of the proposed method, namely, Proportional Error Back-Propagation (PEB), it has been applied to numerous case-studies, which encompass a wide range of experimental conditions, including different scanning trajectories with reversely directed motions within them, and the results are presented. The main contribution of the proposed algorithm is its considerably low computational cost which has the possibility of usage in real-time 3D reconstruction applications. Also, neither manual input nor interference is required from the user, which renders the whole process automatic.

Darko Brodic´, Alessia Amelio, Ivo R. Draganov:

Self-Organizing Map Classification of the Extremely Low-Frequency Magnetic Field Produced by Typical Tablet Computers

Abstract: 

In this paper, the extremely low frequency magnetic field produced by the tablet computers is explored. The measurement of the tablet computers’ magnetic field is performed by using a measuring geometry previously proposed for the laptop computers. The experiment is conducted on five Android tablet computers. The measured values of the magnetic field are compared to the widely accepted TCO safety standard. Then, the results are classified by the Self-Organizing Map method in order to create different levels of safety or danger concerning the magnetic field to which tablet computer users are exposed. Furthermore, a brief comparison of the obtained magnetic field levels with the ones from typical laptops is performed. At the end, a practical suggestion on how to avoid the high exposure to the low frequency magnetic field emitted by the tablet computers is given.

Andrea Malizia, Riccardo Rossi:

Development of a Device to Measure Mass and Resuspension Rate of Dust inside Confined Environments

Abstract: 

A dust explosion is one of the key security issues for many industrial, pharmaceutical and agro-alimentary plants and for the safety of the workers. We have developed an optoelectronic sensor system to determine the mass of deposited dust and the resuspension rate. The authors also mount antennas on an optoelectronic sensor system to perform measurements remotely. The technique used is based on a non-invasive light absorption method. The paper reports a cost analysis in order to demonstrate the possibility to use, in our optoelectronic sensor system, several sensors to monitor large volume. In this paper the authors present the sensor system, the test and calibration of its components together with the results and the error analysis, demonstrating experimentally what is the maximum and the minimum readable range.

Daniel Gogola, Pavol Szomolanyi, Martin Škrátek, Ivan Frollo:

Design and Construction of Novel Instrumentation for Low-Field MR Tomography

Abstract: 

Magnetic resonance imaging (MRI) is a very popular tool for diagnostic applications and research studies. Low-field MR scanners, usually with an open design, are suitable for claustrophobic and obese patients, as well as for children, who may be fearful in closed MR scanners. However, these types of scanners provide lower spatial resolution and a lower signal-to-noise ratio (SNR) if compared with the same examination performed at the same time at high field scanners. It is dominantly caused by the low field strength and other factors, such as radiofrequency noise. Therefore, a long measurement time is usually necessary. This research paper is focused on the development of novel probes and preamplifiers for low-field MR scanners to improve SNR, and thus, shorten the measurement time. In this study, we describe the design of a high impedance preamplifier and a high temperature superconductor (HTS) coil. This novel instrumentation was compared with uncooled and cooled copper coils. Improvement in SNR in the case of an HTS coil is reported.

W. O. Leite, J. C. Campos Rubio, F. Mata, I. Hanafi, A. Carrasco:

Dimensional and Geometrical Errors in Vacuum Thermoforming Products: An Approach to Modeling and Optimization by Multiple Response Optimization

Abstract: 

In the vacuum thermoforming process, the product deviations depend on several parameters of the system, which make the analysis, the computational modeling, and the optimization of errors a multi-variable process with conflicting objectives. In this sense, the aim of this work was to study the dimensional and geometrical errors as well as the optimization (minimization) of these errors in one typical vacuum thermoforming product made of polystyrene (PS). In particular, it was intended to predict and minimize errors in a range of ideal tolerances using Multiple Response Optimization (MRO) Models. Thus, through the fractional factorial design (2^k-p), initial experimental tests were performed using proposed measurement procedures, and Analysis of Variance being the data analysis is discussed. Following that, the MRO models were implemented which were also validated to represent the sample data. Through this analysis of the results, it can be concluded that the regression models of errors are not linear functions, hence, the developed models are valid for the studied process, and finally that the validation results proved the efficiency of MOR models developed, but these models will not be able to generalize to new situations in a range far from the values studied.

Mieczyslaw Korzynski, Kazimiera Dudek, Arkadiusz Palczak, Bartosz Kruczek, Paweł Kocurek:

Experimental Models and Correlations between Surface Parameters after Slide Diamond Burnishing

Abstract: 

In the paper the set of representative parameters for a comprehensive assessment of the surface texture status after slide burnishing has been proposed. The analysis of correlations between the parameters of the surface texture, obtained by slide diamond burnishing of 317Ti steel has been performed. Correlations have been determined and several groups of surface texture parameters with strong mutual correlations (also parameters uncorrelated with the other) have been selected. For both groups of parameters - representative and uncorrelated - experimental mathematical relations defining influences of the input parameters of slide diamond burnishing on the surface texture parameters have been developed. Also, interaction effects for individual parameters of this finishing process have been disclosed. It has been found that by appropriate selection of input conditions of the slide diamond burnishing process, it is possible to obtain a wide range of states of the surface texture.

Top ↑

Measurement of Physical Quantities

Robert Hanus, Adam Kowalczyk, Anna Szlachta, Rafał Chorzępa:

Application of Conditional Averaging to Time Delay Estimation of Random Signals

Abstract: 

The article presents the possibilities of using the function of conditional average value of a delayed signal (CAV) and the function of conditional average value of a delayed signal absolute value (CAAV) to determine the time delay estimation (TDE) of random signals. For discrete CAV and CAAV estimators, the standard uncertainties of the estimation of function values at extreme points and the standard uncertainties of the TDE were given and compared with the corresponding uncertainties for the direct discrete cross-correlation function (CCF) estimator. It was found that the standard uncertainty of TDE for CAV is lower than for CCF independent of signal-to-noise ratio (SNR) for parameter values of a ³ 2 and M/N ³ 0.25 (where: a - relative threshold value, M/N – quotient of number of averaging and number of samples). The standard uncertainty of TDE for CAAV will be lower than for CCF for SNR values greater than 0.35 (for N/M = 1).

Jiong Ding, Suijun Yang, Shuliang Ye:

A Fast-Multi-Channel Sub-Millikelvin Precision Resistance Thermometer Readout Based on the Round-Robin Structure

Abstract: 

The fast response multipoint high-precision temperature measurement is often necessary in many dynamical measurement fields and industrial applications. However, limited by the existing electric circuit architecture, either the AC or DC bridges have the shortcoming that the rates or precisions degenerate markedly in the multi-channel scanning mode. To overcome this disadvantage, a round-robin structural low-cost ratiometric resistance thermometer readout based on several commercial 32-bit sigma-delta analogue-to-digital converters (Σ-Δ ADCs) was presented in this article. The experimental results show that the precision of this readout corresponds to 0.1 mK at 1 Hz when sampling four channel resistors simultaneously, while the precision and rate are not degenerating with the channel number increasing. In addition, the uncertainty of the readout is investigated in this article. It shows that the presented readout can achieve an uncertainty as low as 2.1 mK at 1 Hz (K = 2).

Álvaro P. Raposo:

The Algebraic Structure of Quantity Calculus

Abstract: 

The algebraic structure underlying the quantity calculus is defined axiomatically as an algebraic fiber bundle, that is, a base structure which is a free Abelian group together with fibers which are one dimensional vector spaces, all of them bound by algebraic restrictions. Subspaces, tensor product, and quotient spaces are considered, as well as homomorphisms to end with a classification theorem of these structures. The new structure provides an axiomatic foundation of quantity calculus which is centered on the concept of dimension, rather than on the concept of unit, which is regarded as secondary, and uses only integer exponents of the dimensions.

Václav Nevrlý, Vít Klečka, Michal Vašine, Václav Válek, Jan Suchánek, Michal Dostál, Branislav Hric, Petr Bitala, Zdeněk Zelinger:

A New Line-Shape Asymmetry Model for Wavelength Modulation Spectroscopy in Gaseous Flows

Abstract: 

This communication reports technical notes on the development and application of an automated line-shape fitting procedure for wavelength modulation spectroscopy (WMS). Near-infrared transitions of carbon dioxide (CO2) around 1573 nm were measured in vertical cold (nonreacting) flow of CO2 at atmospheric pressure using WMS with demodulation at second harmonic frequency. Semi-empirical model based on the set of so-called Gabor functions was developed and parameters of Lorentzian line-shape profile and its asymmetry resulting from simultaneous frequency and amplitude response of the current-modulated semiconductor laser were determined. Nonlinear least-square fitting procedure employing differential evolution algorithm was successfully utilized for performing this task. Line-shape fitting procedure enabling efficient signal de-noising and background subtraction of wavelength modulation spectra was implemented into an open-source code.

Miroslav Gutten, Daniel Korenciak, Matej Kucera, Richard Janura, Adam Glowacz, Eliasz Kantoch:

Frequency and Time Fault Diagnosis Methods of Power Transformers

Abstract: 

The authors describe experimental and theoretical analyses of faults of power transformer winding. Faults were caused by mechanical effect of short-circuit currents. Measurements of transformer were carried out in high-voltage laboratory. Frequency and time diagnostic methods (method SFRA - Sweep Frequency Response Analysis, impact test) were used for the analyses. Coils of transformer windings were diagnosed by means of the SFRA method and the time impact test. The analyzed methods had a significant sensitivity to a relatively small deformation of coil. In the analysis a new technique for analyzing the effects of short-circuit currents is introduced. This technique is developed for high-voltage transformers (different types of power). The proposed analyses show that it is necessary to analyze the value of short-circuit current. Short-circuit current represents a danger for the operation of the power transformer. The proposed approach can be used for other types of transformers. Moreover, the presented techniques have a potential application for fault diagnosis of electrical equipment such as: transformers and electrical machines.

Elena Pivarčiová, Daynier Rolando Delgado Sobrino, Yury Rafailovich Nikitin, Radovan Holubek, Roman Ružarovský:

Measuring and Evaluating the Differences of Compared Images for a Correct Car Silhouette Categorization using Integral Transforms

Abstract: 

The present paper focuses on the analysis of the possibilities of using integral transforms for measuring and evaluating the differences of compared images (car silhouettes) with the purpose of a correct car body categorization. Approaches such as the light intensities frequency change, the application of discrete integral transforms without the use of further supplementary information enabling automated data processing using the Fourier-Mellin transforms are used within this work. The calculation of the several metrics was verified through different combinations that implied using and not using the Hamming window and a low-pass filter. The paper introduced a method for measuring and evaluating the differences in the compared images (car silhouettes). The proposed method relies on the fact that the integral transforms have their own transformants in the case of translation, scaling and rotation, in the frequency area. Besides, the Fourier-Mellin transform was to offer image transformation that is resistant to the translation, rotation and scale.

Top ↑

Measurement of Physical Quantities

Imrich Andráš, Pavol Dolinský, Linus Michaeli, Ján Šaliga:

Sparse Signal Acquisition via Compressed Sensing and Principal Component Analysis

Abstract: 

This paper presents a way of acquiring a sparse signal by taking only a limited number of samples; sampling and compression are performed in one step by the analog to information conversion. The signal is recovered with minimal information loss from the reduced data record via compressed sensing reconstruction. Several methods of analog to information conversion are described with focus on numerical complexity and implementation in existing embedded devices. Two novel analog to information conversion methods are proposed, distinctive by their computational simplicity – direct subsampling and subsampling with integration. Proposed sensing methods are intended for and evaluated with real water parameter signals measured by a wireless sensor network. Compressed sensing proves to reduce the data transfer rate by >80 % with very little signal processing performed at the sensing side and no appreciable distortion of the reconstructed signal.

Jun Zhang, Yu Tian, Zongjin Ren, Jun Shao, Zhenyuan Jia:

A Novel Dynamic Method to Improve First-order Natural Frequency for Test Device

Abstract: 

It is important to improve the natural frequency of test device to improve measurement accuracy. First-order frequency is basic frequency of dynamic model, which generally is the highest vibration energy of natural frequency. Taking vector force test device (VFTD) as example, a novel dynamic design method for improving first-order natural frequency by increasing structure stiffness is proposed. In terms of six degree-of-freedom (DOF) of VFTD, dynamic model of VFTD is built through the Lagrange dynamic equation to obtain theoretical natural frequency and mode shapes. Experimental natural frequency obtained by the hammering method is compared with theoretical results to prove rationality of the Lagrange method. In order to improve the stiffness of VFTD, increase natural frequency and meet the requirement of high frequency test, by using the trial and error method combined with curve fitting (TECF), stiffness interval of meeting natural frequency requirement is obtained. Stiffness of VFTD is improved by adopting multiple supports based on the stiffness interval. Improved experimental natural frequency is obtained with the hammering method to show rationality of the dynamic design method. This method can be used in improvement of first-order natural frequency in test structure.

Jiří Přibil, Anna Přibilová, Ivan Frollo:

Analysis of Influence of Coil Gradient System on Vibration Properties and Acoustic Noise Level Generated by the Low Field MRI Device

Abstract: 

The paper focuses on investigation of influence of the volume inserted in the scanning area of the magnetic resonance imaging (MRI) device working with a low magnetic field generated by a pair of permanent magnets on vibration and acoustic noise. In addition, its aim is to evaluate the influence of different types of used scan sequences, different settings of slice orientation and scan parameters on the energy and spectral properties of vibration and noise generated by the gradient coil system of the MRI device. Two basic measurements were performed within this work: mapping of sound pressure levels in the MRI device vicinity and parallel acquisition of vibration signals by sensors mounted on the lower and upper parts of the MRI gradient system. The paper next analyzes changes in properties of the vibration signals for the examined person lying in the scanning area compared with the situation of using only the testing phantom. Spectral characteristics of the recorded vibration signals are then analyzed statistically, and compared visually and numerically. The obtained results of the detailed analysis will be used for improvement of noise suppression algorithms applied to a speech signal recorded simultaneously with scanning of the human vocal tract for its 3D modeling.

Marta Rępalska, Adam Woźniak, Marek Kulus:

Application of Coordinate Measuring Arm for Accurate Measurement of Child Growth

Abstract: 

The article describes an approach to measure child growth using a coordinate measuring arm. For this purpose, a test set up has been built to measure the lower leg length directly on the knee surface and with the help of a plate. The use of the plate resulted in the distribution of pressure on the surface to be measured. Based on the results, the LLV (a lower leg growth velocity) was determined and studies were carried out to estimate the uncertainty of this factor. The obtained LLV results at 0.4 mm/week, correspond to the results of studies conducted on specialist test set-ups for knemometric measures described in the literature. The obtained results also allow recognizing periods of good health and bad health of the child.

Xuewei Wang, Jing Wang:

Pseudorandom Dynamic Test Power Signal Modeling and Electrical Energy Compressive Measurement Algorithm

Abstract: 

With the rapid construction of smart grid, many applications of the new generation and the large power dynamic loads are revolutionizing the electrical energy measurement of electricity meters. The dynamic measurement errors produced by electricity meters are intolerable. In order to solve the dynamic error measurement of electrical energy, firstly, this paper proposes a three-phase pseudorandom dynamic test power signal model to reflect the main characteristics of dynamic loads. Secondly, a compressive measurement algorithm is proposed by the means of steady-state optimization to accurately measure the electrical energy. The experimental results confirm the effectiveness of the three-phase pseudorandom dynamic test signal model, the maximum errors of compressive measurement algorithm are superior to 1×10^-13, the high precision enables the algorithm to accurately measure the electrical energy under different dynamic conditions.

T. Bachorec, P. Fiala, M. Steinbauer, Z. Roubal:

A Non-Destructive Impedance Method Using Resonance to Evaluate the Concentration of Steel Fibers in Concrete

Abstract: 

Steel-fiber reinforced concrete is a composite material characterized by outstanding tensile properties and resistance to cracking. The concrete, however, exhibits such characteristics only on the condition that the steel fibers in the final, hardened composite are distributed evenly. Current methods to evaluate the distribution and concentration in a fiber composite are either destructive or exhibit a limited capability of evaluating the concentration and orientation of the fibers. In this context, the paper discusses auxiliary techniques and laboratory tests that evaluate the density and orientation of the fibers in a composite material, presenting an innovative approach to impedance-based non-destructive testing. The actual methodology utilizes the resonance of the measuring device and the measured sample set; the desired state occurs within the interval of f = 10 kHz and 2 GHz.

Top ↑

Measurement of Physical Quantities

Petra Ráboňová, Gejza Wimmer:

Confidence Region for Calibration Function Coefficients

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.

Oleg Chernoyarov, Alexey Glushkov, Vladimir Litvinenko, Yuliya Litvinenko, Boris Matveev:

Digital Demodulator of the Quadrature Amplitude Modulation Signals

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.

Zhang Ji-wang, Zhang Lai-bin, Ding Ke-Qin, Duan Li-xiang:

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

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.

Tomasz Kowaluk, Maciej Maciak, Adam Woźniak, Piotr Tulik, Natalia Golnik:

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

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.

Gaofa He; Jie Meng; Renbing Tan; Peng Zhong:

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

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.

Ondřej Macíček, Radovan Jiřík, Jan Mikulka, Michal Bartoš, Andrea Šprláková-Puková, Miloš Keřkovský, Zenon Starčuk jr., Karel Bartušek, Torfinn Taxt:

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

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 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.

Top ↑

 No. 1    No. 2    No. 3   No. 4   No. 5   No. 6

Journal is open for your papers

 Download and print the front cover  ->>