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    Wyświetlanie 1-11 z 11
    Tytuł:
    Joint time-frequency and wavelet analysis - an introduction
    Autorzy:
    Majkowski, A.
    Kołodziej, M.
    Rak, R. J.
    Powiązania:
    https://bibliotekanauki.pl/articles/220841.pdf
    Data publikacji:
    2014
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    frequency analysis
    time-frequency analysis
    short-time Fourier transform
    Gabor transform
    Wigner-Ville transform
    Cone-Shaped Transform
    wavelet analysis
    time-scale analysis
    wavelet decomposition
    filter banks
    wavelet packets
    Opis:
    A traditional frequency analysis is not appropriate for observation of properties of non-stationary signals. This stems from the fact that the time resolution is not defined in the Fourier spectrum. Thus, there is a need for methods implementing joint time-frequency analysis (t/f) algorithms. Practical aspects of some representative methods of time-frequency analysis, including Short Time Fourier Transform, Gabor Transform, Wigner-Ville Transform and Cone-Shaped Transform are described in this paper. Unfortunately, there is no correlation between the width of the time-frequency window and its frequency content in the t/f analysis. This property is not valid in the case of a wavelet transform. A wavelet is a wave-like oscillation, which forms its own “wavelet window”. Compression of the wavelet narrows the window, and vice versa. Individual wavelet functions are well localized in time and simultaneously in scale (the equivalent of frequency). The wavelet analysis owes its effectiveness to the pyramid algorithm described by Mallat, which enables fast decomposition of a signal into wavelet components.
    Źródło:
    Metrology and Measurement Systems; 2014, 21, 4; 741-758
    0860-8229
    Pojawia się w:
    Metrology and Measurement Systems
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Brain-computer interface as measurement and control system The review paper
    Autorzy:
    Rak, R. J.
    Kołodziej, M.
    Majkowski, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/221747.pdf
    Data publikacji:
    2012
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    EEG
    brain-computer interface
    feature extraction
    feature selection
    measurement and control
    Opis:
    In the last decade of the XX-th century, several academic centers have launched intensive research programs on the brain-computer interface (BCI). The current state of research allows to use certain properties of electromagnetic waves (brain activity) produced by brain neurons, measured using electroencephalographic techniques (EEG recording involves reading from electrodes attached to the scalp - the non-invasive method - or with electrodes implanted directly into the cerebral cortex - the invasive method). A BCI system reads the user's "intentions" by decoding certain features of the EEG signal. Those features are then classified and "translated" (on-line) into commands used to control a computer, prosthesis, wheelchair or other device. In this article, the authors try to show that the BCI is a typical example of a measurement and control unit.
    Źródło:
    Metrology and Measurement Systems; 2012, 19, 3; 427-444
    0860-8229
    Pojawia się w:
    Metrology and Measurement Systems
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Electrodermal activity measurements for detection of emotional arousal
    Autorzy:
    Kołodziej, M.
    Tarnowski, P.
    Majkowski, A.
    Rak, R. J.
    Powiązania:
    https://bibliotekanauki.pl/articles/200323.pdf
    Data publikacji:
    2019
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    electrodermal activity
    EDA
    galvanic skin response
    GSR
    skin conductance response
    SCR
    feature selection
    arousal
    valence
    classification
    regression
    Opis:
    In this article, we present a comprehensive measurement system to determine the level of user emotional arousal by the analysis of electrodermal activity (EDA). A number of EDA measurements were collected, while emotions were elicited using specially selected movie sequences. Data collected from 16 participants of the experiment, in conjunction with those from personal questionnaires, were used to determine a large number of 20 features of the EDA, to assess the emotional state of a user. Feature selection was performed using signal processing and analysis methods, while considering user declarations. The suitability of the designed system for detecting the level of emotional arousal was fully confirmed, throughout the number of experiments. The average classification accuracy for two classes of the least and the most stimulating movies varies within the range of 61‒72%.
    Źródło:
    Bulletin of the Polish Academy of Sciences. Technical Sciences; 2019, 67, 4; 813-826
    0239-7528
    Pojawia się w:
    Bulletin of the Polish Academy of Sciences. Technical Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Decision Support System for Epileptogenic Zone Location During Brain Resection
    Autorzy:
    Kołodziej, M.
    Majkowski, A.
    Rak, R. J.
    Rysz, A.
    Marchel, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/221787.pdf
    Data publikacji:
    2018
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    ECoG
    iEEG
    electrocorticography
    epileptogenic zone
    signal analysis
    expert system
    neural network
    Opis:
    This paper presents a system for locating the epileptogenic zone (EZ) using an automated analysis of electrocorticography (ECoG) signal recorded with 20 electrodes placed on the brain surface. The developed system enables automatic determination of places where anomalies connected with epilepsy are observed. The developed algorithm was tested on signals recorded for 33 patients who, after a prior neurological analysis, underwent the brain resection surgery. The results obtained with the algorithm were compared with those of medical analyses performed by the neurologist. The proposed system has a satisfactory accuracy – 87.8% – and can be used as a decision-supporting tool by the neurosurgeon during brain resection.
    Źródło:
    Metrology and Measurement Systems; 2018, 25, 1; 15-32
    0860-8229
    Pojawia się w:
    Metrology and Measurement Systems
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Risk analysis of water supply interruptions in collective water supply systems
    Autorzy:
    Tchórzewska-Cieślak, B.
    Rak, J. R.
    Piegdoń, I.
    Powiązania:
    https://bibliotekanauki.pl/articles/2069330.pdf
    Data publikacji:
    2012
    Wydawca:
    Uniwersytet Morski w Gdyni. Polskie Towarzystwo Bezpieczeństwa i Niezawodności
    Tematy:
    water supply
    availability
    risk management
    value of water scarcity
    water production subsystem
    Opis:
    The subject and main purpose of this study is to present the method of risk analysis and assessment of the lack of water supply to the collective water supply system (CWSS). Presented method using the expected value of water scarcity. The analysis was based on all possible states of the operation of water production subsystem. The article contains calculation example of analysis for the exemplary CWSS with regard to absolute risk, equal to the expected value of water scarcity and the relative risk referred to the nominal value of the water demand. In the example attached special importance to the criteria levels of the relative risk of lack of water supply. Presented method is a new concept which allows to make comprehensive analysis of reliability, safety and operation of the collective water supply system.
    Źródło:
    Journal of Polish Safety and Reliability Association; 2012, 3, 2; 201--208
    2084-5316
    Pojawia się w:
    Journal of Polish Safety and Reliability Association
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Baroclinic Rossby radius of deformation in the Southern Baltic Sea
    Autorzy:
    Osinski, R.
    Rak, D.
    Walczowski, W.
    Piechura, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/47732.pdf
    Data publikacji:
    2010
    Wydawca:
    Polska Akademia Nauk. Instytut Oceanologii PAN
    Tematy:
    baroclinic Rossby radius
    deformation
    Baltic Sea
    mesoscale dynamics
    fundamental horizontal scale
    mesoscale process
    Bornholm Basin
    Slupsk Furrow
    Gdansk Basin
    seasonal variability
    saline water
    vertical stratification
    Opis:
    The first baroclinic Rossby radius of deformation (R1) is a fundamental horizontal scale of mesoscale processes. This scale is important for planning both numerical modelling and study areas. R1 was computed on the basis of an 11-year series of high resolution CTD measurements collected during r/v ‘Oceania’ cruises. The data set covered the three main basins of the Baltic Proper: the Bornholm Basin (BB), the Słupsk Furrow (SF) and the Gdańsk Basin (GB). The smallest mean value of R1 was found in the Gdańsk Basin (5.2 km), the largest one in the Bornholm Deep (7.3 km). The seasonal variability of R1 is lower in the western basin than in the eastern one. The seasonal cycle of R1 may be broken by extreme events, e.g. main Baltic inflows (MBI) of saline water. The inflowing water rebuilds the vertical stratification in the southern Baltic Sea and dramatically changes the R1 values. The difference of R1 between a stagnation period and an inflow situation is shown on the basis of observations made during 2002–2003. The main inflow occurred in winter, after ten years of stagnation, and the very low values of R1 (about 4 km) changed to very high ones (more than 9 km). Analysis of stagnation and saltwater inflow events may throw light on the value of R1 in future climatic scenarios. The potential influence of climate change on Baltic Sea salinity, especially a decrease in MBI activity, may change the baroclinic Rossby radius of deformation and the mesoscale dynamics. Values of R1 are expected to be lower in the future climate than those measured nowadays.
    Źródło:
    Oceanologia; 2010, 52, 3; 417-429
    0078-3234
    Pojawia się w:
    Oceanologia
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Failure risk analysis in the water supply sector management
    Autorzy:
    Tchórzewska-Cieślak, B.
    Rak, J. R.
    Pietrucha, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/2069627.pdf
    Data publikacji:
    2011
    Wydawca:
    Uniwersytet Morski w Gdyni. Polskie Towarzystwo Bezpieczeństwa i Niezawodności
    Tematy:
    water supply
    risk management
    safety
    critical infrastructure
    Opis:
    The subject and main purpose of this study is to develop risk analytic model for the design and operation of water supply sector. A water supply system belongs to the critical infrastructure of cities, and it should be a priority task for waterworks and even for the local authorities to ensure the suitable level of its safety. A water supply systems (WSS) ought to be high reliable continuous operating system. Failure factors in WSS should be identified and prioritized, for example, the causing factors in the most frequent failures in waterpipe network. Drinking water supply utilities are responsible for providing a safe and reliable supply of potable water to their customers. Risk priority helps asset manager to target and refine maintenance plans, capital expenditure plans, investigative activities, and deal with potential failure before it occurs. In this paper, we present a review of classic risk analyses, risk management and new methodology for water supply networks management. This paper presents a framework for the analysis of performance risk in water supply that can be applied to the entire system or to individual subsystems. It is expecting that the methodology for the water supply performance risk analysis would provide the city leadership for decision making support.
    Źródło:
    Journal of Polish Safety and Reliability Association; 2011, 2, 1; 185--196
    2084-5316
    Pojawia się w:
    Journal of Polish Safety and Reliability Association
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Cross-Correlations in Warsaw Stock Exchange
    Autorzy:
    Rak, R.
    Kwapień, J.
    Oświęcimka, P.
    Drożdż, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/1812226.pdf
    Data publikacji:
    2008-09
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    89.20.-a
    89.65.Gh
    89.75.-k
    Opis:
    We study the inter-stock correlations for the largest companies listed on Warsaw Stock Exchange and included in the WIG20 index. Our results from the correlation matrix analysis indicate that the Polish stock market can be well described by a one-factor model. We also show that the stock- stock correlations tend to increase with the timescale of returns and they approach a saturation level for the timescales of at least 200 min, i.e. an order of magnitude longer than in the case of some developed markets. We also show that the strength of correlations among the stocks crucially depends on their capitalization. These results combined with our earlier findings together suggest that now the Polish stock market situates itself somewhere between an emerging market phase and a mature market phase.
    Źródło:
    Acta Physica Polonica A; 2008, 114, 3; 561-568
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Safety analysis of water supply systems including protection barriers
    Autorzy:
    Pietrucha-Urbanik, K.
    Rak, J. R.
    Tchórzewska-Cieślak, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/2069151.pdf
    Data publikacji:
    2013
    Wydawca:
    Uniwersytet Morski w Gdyni. Polskie Towarzystwo Bezpieczeństwa i Niezawodności
    Tematy:
    water supply system
    protection barriers
    event tree
    Opis:
    Water quality control from the perspective of water supply system users’ safety contributed to create drinking water production and quality control procedures. Contemporary risk hazard analysis should be performed on the stage of production, distribution and storage of tap water. Sequences of undesirable events are considered in the so-called waterworks chain series. This leads to critical control points and gives the ability to provide current control over the processes in the collective water supply system, as well as of their combinations and mutual interactions. Methodology of water consumers protection against incidental pollutions was shown. Algorithm concerning identification of critical control points – CCP was developed .The rules of safety related system into drinking water production have been shown. Also risk assessment using the tree event method was presented.
    Źródło:
    Journal of Polish Safety and Reliability Association; 2013, 4, 2; 241--248
    2084-5316
    Pojawia się w:
    Journal of Polish Safety and Reliability Association
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effect of creep on crystallographic orientation in single crystal superalloy
    Autorzy:
    Albrecht, R.
    Rak, J.
    Bogdanowicz, W.
    Gancarczyk, K.
    Sieniawski, J.
    Kubiak, K.
    Lelątko, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1075665.pdf
    Data publikacji:
    2016-10
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.72.Ff
    81.10.Aj
    61.72.Hh
    Opis:
    The creep-rupture tests were performed on a single crystal rods made of CMSX-4 superalloy obtained at withdrawal rates of 3 and 5 mm/min. After the rupture the microstructure and fracture surface were examined and correlated with X-ray crystal rotation measurements by the Ω-scan method. The conclusions about the crystal lattice rotation during creep test were provided.
    Źródło:
    Acta Physica Polonica A; 2016, 130, 4; 1094-1096
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Different Fractal Properties of Positive and Negative Returns
    Autorzy:
    Oświęcimka, P.
    Kwapień, J.
    Górski, A.
    Drożdż, S.
    Rak, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/1812224.pdf
    Data publikacji:
    2008-09
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    89.20.-a
    89.65.Gh
    Opis:
    We perform an analysis of fractal properties of the positive and the negative changes of the German DAX30 index separately using multifractal detrended fluctuation analysis. By calculating the singularity spectra f(α) we show that returns of both signs reveal multiscaling. Curiously, these spectra display a significant difference in the scaling properties of returns with opposite sign. The negative price changes are ruled by stronger temporal correlations than the positive ones, which is manifested by larger values of the corresponding Hölder exponents. As regards the properties of dominant trends, a bear market is more persistent than the bull market irrespective of the sign of fluctuations.
    Źródło:
    Acta Physica Polonica A; 2008, 114, 3; 547-553
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-11 z 11

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