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Number of results: 795
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Abstract

The upcoming hypersonic technologies pose a difficult task for air navigation systems. The article presents a designed model of elastic interaction of penetrating acoustic radiation with flat isotropic suspension elements of an inertial navigation sensor in the operational conditions of hypersonic flight. It has been shown that the acoustic transparency effect in the form of a spatial-frequency resonance becomes possible with simultaneous manifestation of the wave coincidence condition in the acoustic field and equality of the natural oscillation frequency of a finite-size plate and a forced oscillation frequency of an infinite plate. The effect can lead to additional measurement errors of the navigation system. Using the model, the worst and best case suspension oscillation frequencies can be determined, which will help during the design of a navigation system.

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Authors and Affiliations

Igor Korobiichuk
Volodimir Karachun
Viktorij Mel’nick
Maciej Kachniarz
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Abstract

The suitability of low-cost impedance sensors for microbiological purposes and biofilm growth monitoring was evaluated. The sensors with interdigitated electrodes were fabricated in PCB and LTCC technologies. The electrodes were golden (LTCC) or gold-plated (PCB) to provide surface stability. The sensors were used for monitoring growth and degradation of the reference ATCC 15442 Pseudomonas aeruginosa strain biofilm in invitro setting. During the experiment, the impedance spectra of the sensors were measured and analysed using electrical equivalent circuit (EEC) modelling. Additionally, the process of adhesion and growth of bacteria on a sensor’s surface was assessed by means of the optical and SEM microscopy. EEC and SEM microscopic analysis revealed that the gold layer on copper electrodes was not tight, making the PCB sensors susceptible to corrosion while the LTCC sensors had good surface stability. It turned out that the LTCC sensors are suitable for monitoring pseudomonal biofilm and the PCB sensors are good detectors of ongoing stages of biofilm formation.

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Authors and Affiliations

Konrad Chabowski
Adam F. Junka
Tomasz Piasecki
Damian Nowak
Karol Nitsch
Danuta Smutnicka
Marzenna Bartoszewicz
Magdalena Moczała
Patrycja Szymczyk
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Abstract

EEG signal-based sleep stage classification facilitates an initial diagnosis of sleep disorders. The aim of this study was to compare the efficiency of three methods for feature extraction: power spectral density (PSD), discrete wavelet transform (DWT) and empirical mode decomposition (EMD) in the automatic classification of sleep stages by an artificial neural network (ANN). 13650 30-second EEG epochs from the PhysioNet database, representing five sleep stages (W, N1-N3 and REM), were transformed into feature vectors using the aforementioned methods and principal component analysis (PCA). Three feed-forward ANNs with the same optimal structure (12 input neurons, 23 + 22 neurons in two hidden layers and 5 output neurons) were trained using three sets of features, obtained with one of the compared methods each. Calculating PSD from EEG epochs in frequency sub-bands corresponding to the brain waves (81.1% accuracy for the testing set, comparing with 74.2% for DWT and 57.6% for EMD) appeared to be the most effective feature extraction method in the analysed problem.

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Authors and Affiliations

Monika Prucnal
Adam G. Polak
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Abstract

High temperature and high electric field applications in tantalum and niobium capacitors are limited by the mechanism of ion migration and field crystallization in a tantalum or niobium pentoxide insulating layer. The study of leakage current (DCL) variation in time as a result of increasing temperature and electric field might provide information about the physical mechanism of degradation. The experiments were performed on tantalum and niobium oxide capacitors at temperatures of about 125°C and applied voltages ranging up to rated voltages of 35 V and 16 V for tantalum and niobium oxide capacitors, respectively. Homogeneous distribution of oxygen vacancies acting as positive ions within the pentoxide layer was assumed before the experiments. DCL vs. time characteristics at a fixed temperature have several phases. At the beginning of ageing the DCL increases exponentially with time. In this period ions in the insulating layer are being moved in the electric field by drift only. Due to that the concentration of ions near the cathode increases producing a positively charged region near the cathode. The electric field near the cathode increases and the potential barrier between the cathode and insulating layer decreases which results in increasing DCL. However, redistribution of positive ions in the insulator layer leads to creation of a ion concentration gradient which results in a gradual increase of the ion diffusion current in the direction opposite to the ion drift current component. The equilibrium between the two for a given temperature and electric field results in saturation of the leakage current value. DCL vs. time characteristics are described by the exponential stretched law. We found that during the initial part of ageing an exponent n = 1 applies. That corresponds to the ion drift motion only. After long-time application of the electric field at a high temperature the DCL vs. time characteristics are described by the exponential stretched law with an exponent n = 0.5. Here, the equilibrium between the ion drift and diffusion is achieved. The process of leakage current degradation is therefore partially reversible. When the external electric field is lowered, or the samples are shortened, the leakage current for a given voltage decreases with time and the DCL vs. time characteristics are described by the exponential stretched law with an exponent n = 0.5, thus the ion redistribution by diffusion becomes dominant.

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Authors and Affiliations

Martin Kuparowitz
Lubomír Grmela
Vlasta Sedlakova
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Abstract

Many precision devices, especially measuring devices, must maintain their technical parameters in variable ambient conditions, particularly at varying temperatures. Examples of such devices may be super precise balances that must keep stability and accuracy of the readings in varying ambient temperatures. Due to that fact, there is a problem of measuring the impact of temperature changes, mainly on geometrical dimensions of fundamental constructional elements of these devices. In the paper a new system for measuring micro-displacements of chosen points of a constructional element of balance with a resolution of single nanometres and accuracy at a level of fractions of micrometres has been proposed.

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Authors and Affiliations

Marek Dobosz
Adam Woźniak
Mariusz Kożuchowski
Marek Ściuba
Olga Iwasińska-Kowalska
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Abstract

This paper describes the use of new methods of detecting faults in medium-voltage overhead lines built of covered conductors. The methods mainly address such faults as falling of a conductor, contacting a conductor with a tree branch, or falling a tree branch across three phases of a medium-voltage conductor. These faults cannot be detected by current digital relay protection systems. Therefore, a new system that can detect the above mentioned faults was developed. After having tested its operation, the system has already been implemented to protect mediumvoltage overhead lines built of covered conductors.

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Authors and Affiliations

Stanislav Mišák
Štefan Hamacek
Mikołaj Bartłomiejczyk
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Abstract

This work examines the reduced-cost design optimization of dual- and multi-band antennas. The primary challenge is independent yet simultaneous control of the antenna responses at two or more frequency bands. In order to handle this task, a feature-based optimization approach is adopted where the design objectives are formulated on the basis of the coordinates of so-called characteristic points (or response features) of the antenna response. Due to only slightly nonlinear dependence of the feature points on antenna geometry parameters, optimization can be attained at a low computational cost. Our approach is demonstrated using two antenna structures with the optimum designs obtained in just a few dozen of EM simulations of the respective structure.

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Authors and Affiliations

Sławomir Kozieł
Adrian Bekasiewicz
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Abstract

The paper presents a method of developing a variable structure measurement system with intelligent components for flight vehicles. In order to find a distinguishing feature of a variable structure, a numerical criterion for selecting measuring sensors is proposed by quantifying the observability of different states of the system. Based on the Peter K. Anokhin’s theory of functional systems, a mechanism of “action acceptor” is built with intelligent components, e.g. self-organization algorithms. In this mechanism, firstly, prediction models of system states are constructed using self-organization algorithms; secondly, the predicted and measured values are compared; thirdly, an optimal structure of the measurement system is finally determined based on the results of comparison. According to the results of simulation with practical data and experiments obtained during field tests, the novel developed measurement system has the properties of high-accuracy, reliable operation and fault tolerance.

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Authors and Affiliations

Kai Shen
Maria S. Selezneva
Konstantin A. Neusypin
Andrey V. Proletarsky
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Abstract

Single-frame methods of determining the attitude of a nanosatellite are compared in this study. The methods selected for comparison are: Single Value Decomposition (SVD), q method, Quaternion ESTimator (QUEST), Fast Optimal Attitude Matrix (FOAM) − all solving optimally the Wahba’s problem, and the algebraic method using only two vector measurements. For proper comparison, two sensors are chosen for the vector observations on-board: magnetometer and Sun sensors. Covariance results obtained as a result of using those methods have a critical importance for a non-traditional attitude estimation approach; therefore, the variance calculations are also presented. The examined methods are compared with respect to their root mean square (RMS) error and variance results. Also, some recommendations are given.

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Authors and Affiliations

Demet Cilden Guler
Ece S. Conguroglu
Chingiz Hajiyev
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Abstract

This paper presents an alternative approach to the sequential data classification, based on traditional machine learning algorithms (neural networks, principal component analysis, multivariate Gaussian anomaly detector) and finding the shortest path in a directed acyclic graph, using A* algorithm with a regression-based heuristic. Palm gestures were used as an example of the sequential data and a quadrocopter was the controlled object. The study includes creation of a conceptual model and practical construction of a system using the GPU to ensure the realtime operation. The results present the classification accuracy of chosen gestures and comparison of the computation time between the CPU- and GPU-based solutions.

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Authors and Affiliations

Marek Wodziński
Aleksandra Krzyżanowska
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Abstract

HPM meters are required for the assessment of fields generated by sources of high-power microwaves. Finding the inverse calibration curves for such instruments is important for ensuring accuracy. The procedure is relatively simple for meters consisting of linear devices but there can also be hardware solutions implementing nonlinear ones. The objective of the present work was to develop a convenient procedure to allow finding such a curve when the meter uses a D-dot probe and a power detector. For that purpose, the results of low voltage measurements describing the properties of the detector were first analysed. Then a software code was developed to estimate the RMS value of an incident field based on measured output and frequency response. The response was estimated with very low electric field. And finally, the performance of the proposed procedure was verified by tests conducted with high electric field in a TEM cell. High conformity of the output of the meter with fields of known values was demonstrated. The maximum error related to the meter range did not exceed 4%.

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Authors and Affiliations

Jacek Jakubowski
ORCID: ORCID
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Abstract

The objective of the study was to assess the potential use of optical measuring instruments to determine the minimum chip thickness in face milling. Images of scanned surfaces were analyzed using mother wavelets. Filtration of optical signals helped identify the characteristic zones observed on the workpiece surface at the beginning of the cutting process. The measurement data were analyzed statistically. The results were then used to estimate how accurate each measuring system was to determine the minimum uncut chip thickness. Also, experimental verification was carried out for each mother wavelet to assess their suitability for analyzing surface images.

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Authors and Affiliations

Damian Gogolewski
Włodzimierz Makieła
Łukasz Nowakowski
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Abstract

We present spectral emission characteristics from laser-plasma EUV/SXR sources produced by irradiation of < 1 J energy laser pulse on eleven different double stream gas puff targets, with most intense electronic transitions identified in the spectral range from 1 nm to 70 nm wavelength which corresponds to photon energy from 18 eV to 1240 eV. The spectra were obtained using grazing incidence and transmission spectro- graphs from laser-produced plasma emission, formed by the interaction of a laser beam with a double stream gas puff target. Laser pulses with a duration of 4 ns and energy of 650 mJ were used for the experiment. We present the results obtained from three different spectrometers in the wavelength ranges of SXR (1–5.5 nm), SXR/EUV (4–15.5 nm), and EUV (10–70 nm). In this paper, detailed information about the source, gas targets under investigation, the experimental setup, spectral measurements and the results are presented and discussed. Such data may be useful for the identification of adequate spectral emissions from gasses in the EUV and SXR wavelength ranges dedicated to various experiments (i.e. broadband emission for the X-ray coherence tomography XCT) or may be used for verification of magnetohydrodynamic plasma codes.

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Authors and Affiliations

Antony Jose Arikkatt
Przemysław Wachulak
Henryk Fiedorowicz
Andrzej Bartnik
Joanna Czwartos
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Abstract

The article presents methodology for testing the electric strength of vacuum chambers designed for modern medium voltage switchgear developed by the authors, using two innovative test stands designed and constructed by the research team above. Verification of the correctness of operation of the test stands, as well as the validity of the developed methodology was carried out by performing a series of tests. It was determined that below certain pressure values in the tested chamber (from about 5.0×10 0 Pa for station 1 and for about 4.0×10 -1 Pa for station 2), the electric strength maintains a constant value, which guarantees stable operation of the vacuum chamber. The values of the total measurement uncertainty for the electric strength tests were also estimated.

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Authors and Affiliations

Paweł Węgierek
ORCID: ORCID
Michał Lech
ORCID: ORCID
Czesław Kozak
Justyna Pastuszak
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Abstract

The Lithuanian national standard of electric resistance is maintained as the basis for calibration and measurement capabilities published in the key comparison database of the International Bureau of Weights and Measures (BIPM). The stability and uncertainty of the resistance value measurements, performed since 2004 using the calibrated values of the standard resistors to predict their future behaviour as well as influence of environmental conditions, are discussed. Also discussed is the recovery of a standard resistor which had undergone a mechanical disturbance. It is concluded that the standard resistors operated by the Lithuanian National Electrical Standards Laboratory feature stable drift of resistance, which is well predicted by means of linear regression.

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Authors and Affiliations

Andrius Bartašiunas
Rimantas Miškinis
Dmitrij Smirnov
Emilis Urba
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Abstract

Virtual reality (VR) has become a realistic alternative to conventional learning methods in numerous fields including military training. Accurate and precise tracking of a user wearing a head-mounted display is necessary to achieve an immersive VR experience. The widely available SteamVR system, where licensed users can design and construct trackers optimized for a given application can be an alternative to very expensive professional motion tracking. This paper presents the complete design process of a SteamVR tracker dedicated to a shooting simulation in a VR environment.We describe the optimization and simulation of the tracker’s shape and configuration of the sensors. In the simulation phase the developed model had better parameters than its commercial counterparts. Next, the optimized prototype was constructed and configured. The dedicated and automated measuring arrangement provided experimental verification of the tracker’s performance. Tracking performance as well as the accuracy and precision of both position and orientation measurements were determined and compared with simulations, which proved that the simulation software can accurately predict selected properties of the proposed tracker.

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Authors and Affiliations

Marcin Maciejewski
Marek Piszczek
Mateusz Pomianek
Norbert Pałka
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Abstract

Electrified railways are an example of AC single phase distribution networks. A non-negligible amount of active and nonactive power may be related to harmonics, especially for distorted highly-loaded systems. The paper considers the relevance of the harmonic power terms in order to identify distortion sources in a single-point perspective, in line with the approach of EN 50463 for the quantification of the power and energy consumption. Some single-point Harmonic Producer Indicators (HPI) based on harmonic active power direction and nonactive distortion power terms are reviewed and evaluated using pantograph voltage and current measured during several hours of runs in two European AC railways (operated at 16.7 and 50 Hz). The HPI based on active power shows to be consistent and provides detailed information of rolling stock characteristic components under variable operating conditions; those based on nonactive distortion power are global indexes and hardly can operate with complex harmonic patterns in variable operating conditions.

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Authors and Affiliations

Andrea Mariscotti
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Abstract

The paper presents a detailed theoretical background for coordinate measurement uncertainty evaluation by means of Type B evaluation method, taking into account information on accuracy of a coordinate measuring system given with the formula for maximum permissible errors of length measurement and verification test results. A proposal for evaluation of the verification test results is made. A measurement model based on the point-plane distance equation is presented. A detailed analysis of the partial derivatives (sensitivity factors in an uncertainty budget) of the measurement model is presented. The analyses of measurement uncertainty for different geometrical characteristicswere conducted using this measurement model. Examples of uncertainty evaluation for geometrical deviations are presented: position of a point related to a datum plane and flatness in the case of convex or concave surfaces. The examples include detailed uncertainty budgets.

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Authors and Affiliations

Wojciech Płowucha
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Abstract

The paper examines the usage of Convolutional Bidirectional Recurrent Neural Network (CBRNN) for a problem of quality measurement in a music content. The key contribution in this approach, compared to the existing research, is that the examined model is evaluated in terms of detecting acoustic anomalies without the requirement to provide a reference (clean) signal. Since real music content may include some modes of instrumental sounds, speech and singing voice or different audio effects, it is more complex to analyze than clean speech or artificial signals, especially without a comparison to the known reference content. The presented results might be treated as a proof of concept, since some specific types of artefacts are covered in this paper (examples of quantization defect, missing sound, distortion of gain characteristics, extra noise sound). However, the described model can be easily expanded to detect other impairments or used as a pre-trained model for other transfer learning processes. To examine the model efficiency several experiments have been performed and reported in the paper. The raw audio samples were transformed into Mel-scaled spectrograms and transferred as input to the model, first independently, then along with additional features (Zero Crossing Rate, Spectral Contrast). According to the obtained results, there is a significant increase in overall accuracy (by 10.1%), if Spectral Contrast information is provided together with Mel-scaled spectrograms. The paper examines also the influence of recursive layers on effectiveness of the artefact classification task.

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Authors and Affiliations

Kamila Organiściak
Józef Borkowski
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Abstract

This article concerns a new method of assessing the thread cutting process and the quality of the formed thread using the method of optical observation of the workpiece during machining. A series of digital images of the thread profile was taken in transmitted light for each tool infeed. Such images, obtained with high resolution for three angular positions, were binarized, with the space between ridges taken in successive infeeds identified as “void”, and its projection was then parameterized. Two of these parameters, area of void and aspect ratio, were used as indicators of the technological quality of the thread. The suitability of the selected parameters for technological description of the thread was verified using the example of titanium alloy thread turning under ambient and cryogenic conditions.

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Authors and Affiliations

Anna Zawada-Tomkiewicz
Łukasz Żurawski
Dariusz Tomkiewicz
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Abstract

It is now widely recognized that the evaluation of the uncertainty associated with a result is an essential part of any quantitative analysis. One way to use the estimation of measurement uncertainty as a metrological critical evaluation tool is the identification of sources of uncertainty on the analytical result, knowing the weak steps, in order to improve the method, when it is necessary. In this work, this methodology is applied to fuel analyses and the results show that the relevant sources of uncertainty are: beyond the repeatability, the resolution of the volumetric glassware and the blank in the analytical curve that are little studied.

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Authors and Affiliations

Elcio de Oliveira
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Abstract

The paper presents a proposal of using additional statistical parameters such as: standard deviation, variance, maximum and minimum increases of the observed value that were determined during measurements of temperature fields created on the surface of the tested electrochemical capacitor. The measurements were carried out using thermographic methods in order to support assessment of the condition of electrochemical capacitor under classic durability tests based on methods of determination of capacity and equivalent series resistance. The possibility of using some statistical parameters in assessment of the electrochemical capacitor quality was illustrated. The applied measurement methodology and the results of research associated with the classic methods of supercapacitors’ assessment are presented. The obtained results indicate that the variability of some statistical parameters of temperature fields can be directly related to changing the values of standard parameters describing electrochemical capacitor, which are capacitance and equivalent series resistance.

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Authors and Affiliations

Stanisław Galla
Arkadiusz Szewczyk
Łukasz Lentka
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Abstract

The paper presents definitions and relative measures of the system sensitivity and sensitivity of its errors. The model of a real system and model of an ideal measuring system were introduced. It allows to determine the errors of the system. The paper presents also how to use the error sensitivity analysis carried out on the models of the measuring system to the correction of the nonlinearity error of its static characteristic. The corrective function is determined as a relation between the input variable of the tested system and its chosen parameter. The use of the proposed method has been presented on the example of a phase angle modulator. The obtained results have been compared with the results of analytic calculations. The idea of a phase angle modulator is also presented.

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Authors and Affiliations

Ryszard Sroka
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Abstract

In this paper, an experimental surface roughness analysis in milling of tungsten carbide using a monolithic torus cubic boron nitride (CBN) tool is presented. The tungsten carbide was received using direct laser deposition technology (DLD). The depth of cut (ap), feed per tooth (fz) and tool wear (VBc) influence on surface roughness parameters (Ra, Rz) were investigated. The cutting forces and accelerations of vibrations were measured in order to estimate their quantitative influence on Ra and Rz parameters. The surface roughness analysis, from the point of view of milling dynamics was carried out. The dominative factor in the research was not feed per tooth fz (according to a theoretical model) but dynamical phenomena and feed per revolution f connected with them.

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Authors and Affiliations

Paweł Twardowski

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