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    Wyświetlanie 1-12 z 12
    Tytuł:
    Differences in the relationship between bacterial count decay and storage time in Antarctic freshwater samples
    Autorzy:
    Allende, Luz
    Powiązania:
    https://bibliotekanauki.pl/articles/2051915.pdf
    Data publikacji:
    2006
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    Antarctica
    bacterioplankton
    count decay
    storage
    Źródło:
    Polish Polar Research; 2006, 27, 1; 63-69
    0138-0338
    2081-8262
    Pojawia się w:
    Polish Polar Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Transient stability analysis and control of power systems with considering flux decay by energy function approach
    Autorzy:
    Lu, D.
    Zhang, X.
    Powiązania:
    https://bibliotekanauki.pl/articles/201016.pdf
    Data publikacji:
    2012
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    transient stability
    dynamic performance
    flux decay
    structure preserving models
    energy function
    Opis:
    In this paper, transient stability of power systems with structure preserving models is considered. A Hamiltonian function which can be regarded as a Lyapunov function for the system is proposed. Based on this, the influence of flux decay dynamics, especially during a fault, on transient stability is analyzed. With the increase of load power, the variation of stability boundary in the rotor angle/Eq plane is shown. The Energy-based excitation control, aiming at injecting additional damping into the post-fault system may reduce the critical clearing time (CCT). This can be demonstrated by the comparison of different flux decay dynamics in the fault-on condition, and the reason is illustrated by the relationship between rotor angle/Eq and the stability boundary. An improved control strategy is proposed and applied to increase the CCT. Simulation results verify that improvement is obtained both in transient stability and dynamic performance.
    Źródło:
    Bulletin of the Polish Academy of Sciences. Technical Sciences; 2012, 60, 1; 3-8
    0239-7528
    Pojawia się w:
    Bulletin of the Polish Academy of Sciences. Technical Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Evaluation of Decay Times from Noisy Room Responses with Pure-Tone Excitation
    Autorzy:
    Meissner, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/177891.pdf
    Data publikacji:
    2013
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    room acoustics
    reverberation
    decay times
    room response
    background noise
    coupled rooms
    Opis:
    Reverberant responses are widely used to characterize acoustic properties of rooms, such as the early decay time (EDT) and the reverberation times T20 and T30. However, in real conditions a sound decay is often deformed by background noise, thus a precise evaluation of decay times from noisy room responses is the main problem. In this paper this issue is examined by means of numerical method where the decay times are estimated from the decay function that has been determined by nonlinear polynomial regression from a pressure envelope obtained via the discrete Hilbert transform. In numerical experiment the room responses were obtained from simulations of a sound decay for two-room coupled system. Calculation results have shown that background noise slightly affects the evaluation of reverberation times T20 and T30 as long as the signal-to-noise ratio (SNR) is not smaller than about 25 and 35 dB, respectively. However, when the SNR is close to about 20 and 30 dB, high overestimation of these times may occur as a result of bending up of the decay curve during the late decay.
    Źródło:
    Archives of Acoustics; 2013, 38, 1; 47-54
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Exponential decay of transient values in discrete-time positive nonlinear systems
    Autorzy:
    Kaczorek, Tadeusz
    Ruszewski, Andrzej
    Powiązania:
    https://bibliotekanauki.pl/articles/2175100.pdf
    Data publikacji:
    2022
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    exponential decay
    transient value
    discrete-time
    fractional order
    positive
    nonlinear
    feedback
    system
    Opis:
    The exponential decay of transient values in discrete-time nonlinear standard and fractional orders systems with linear positive linear part and positive feedbacks is investigated. Sufficient conditions for the exponential decay of transient values in this class of positive nonlinear systems are established. A procedure for computation of gains characterizing the class of nonlinear elements are given and illustrated on simple example.
    Źródło:
    Archives of Control Sciences; 2022, 32, 3; 577--588
    1230-2384
    Pojawia się w:
    Archives of Control Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Prediction of Reverberant Properties of Enclosures via a Method Employing a Modal Representation of the Room Impulse Response
    Autorzy:
    Meissner, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/177946.pdf
    Data publikacji:
    2016
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    room acoustics
    indoor reverberation
    room impulse response
    modal expansion method
    decay times
    Opis:
    A theoretical method has been presented to describe sound decay in enclosures and simulate the room impulse response (RIR) employed for prediction of the indoor reverberation characteristics. The method was based on a solution of wave equation with the form of a series whose time-decaying components represent responses of acoustic modes to an impulse sound source. For small sound absorption on room walls this solution was found by means of the method of variation of parameters. A decay function was computed via the time-reverse integration of the squared RIR. Computer simulations carried out for a rectangular enclosure have proved that the RIR function reproduces the structure of a sound field in the initial stage of sound decay sufficiently well. They have also shown that band-limitedness of the RIR has evident influence on the shape of the decay function and predicted decay times.
    Źródło:
    Archives of Acoustics; 2016, 41, 1; 27-41
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Chosen properties of oak wood immersed for 6 months in the Baltic Sea
    Autorzy:
    Fojutowski, A.
    Wroblewska, H.
    Kropacz, A.
    Komorowicz, M.
    Noskowiak, A.
    Pomian, I.
    Powiązania:
    https://bibliotekanauki.pl/articles/29858.pdf
    Data publikacji:
    2011
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    chosen property
    oak wood
    Baltic Sea
    strength
    fungi
    decay
    chemical composition
    archaeological wood
    Opis:
    Changes of physical and chemical properties, mass loss and susceptibility of oak wood to decay caused by Basidiomycetes fungi were assessed after wood samples had been taken out of the sea within the framework of MACHU project. Test samples of oak wood of the dimensions of 250 × 10 × 10 mm were placed in coastal waters of the Baltic Sea at the area of medieval seaport in Puck and in waters of the Gdansk Bay at the same longitude as Orłowo (near the wreck of Swedish warship Solen). The samples taken out of the sea were examined visually and described. Changes in mass of the samples, their bending strength and modulus of elasticity, compression strength along the grain, ability to decay caused by Trametes versicolor fungus, content of mineral substances and substances soluble in water, ethanol-benzene mixture and in 1-percent aqueous solution of NaOH, content of cellulose, lignin and pentosanes as well as pH of the wood were investigated. The properties of samples taken out of the sea after 6 months of immersion were compared with the properties of control twin samples of oak wood which had not been immersed. The results obtained so far indicate that noticeable, measurable changes in oak wood immersed in sea occur already in half a year since immersion, so observation of them may be useful for protection and monitoring of underwater archaeological objects.
    Źródło:
    Folia Forestalia Polonica. Series B - Drzewnictwo; 2011, 42
    0071-6685
    Pojawia się w:
    Folia Forestalia Polonica. Series B - Drzewnictwo
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A Revised Sound Energy Theory Based on a New Formula for the Reverberation Radius in Rooms with Non-Diffuse Sound Field
    Autorzy:
    Arau-Puchades, H.
    Berardi, U.
    Powiązania:
    https://bibliotekanauki.pl/articles/177958.pdf
    Data publikacji:
    2015
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    reverberation radius
    critical distance
    non-diffuse sound field
    sound energy
    revised sound decay theory
    Opis:
    This paper discusses the concept of the reverberation radius, also known as critical distance, in rooms with non-uniformly distributed sound absorption. The reverberation radius is the distance from a sound source at which the direct sound level equals the reflected sound level. The currently used formulas to calculate the reverberation radius have been derived by the classic theories of Sabine or Eyring. However, these theories are only valid in perfectly diffused sound fields; thus, only when the energy density is constant throughout a room. Nevertheless, the generally used formulas for the reverberation radius have been used in any circumstance. Starting from theories for determining the reverberation time in non-diffuse sound fields, this paper firstly proposes a new formula to calculate the reverberation radius in rooms with non-uniformly distributed sound absorption. Then, a comparison between the classic formulas and the new one is performed in some rectangular rooms with non-uniformly distributed sound absorption. Finally, this paper introduces a new interpretation of the reverberation radius in non-diffuse sound fields. According to this interpretation, the time corresponding to the sound to travel a reverberation radius should be assumed as the lower limit of integration of the diffuse sound energy.
    Źródło:
    Archives of Acoustics; 2015, 40, 1; 33-40
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Uncertainty of the magnetic flux linkage measurements performed by modified current decay test
    Autorzy:
    Kowalik, Z.
    Powiązania:
    https://bibliotekanauki.pl/articles/141517.pdf
    Data publikacji:
    2017
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    flux linkage measurements
    modified current decay test
    uncertainty of integral calculations
    uncertainty of simplicial approximation
    Opis:
    The paper presents the estimation methodology for uncertainties of magnetic flux linkage measurements, when the flux linkage and current functions with respect to time are obtained instead of single values of these quantities. The computed uncertainties are then used to estimate the quality of an approximation of a current-flux characteristic in the mathematical model of an electrical machine when the approximation is based on the results of measurements.
    Źródło:
    Archives of Electrical Engineering; 2017, 66, 3; 643-653
    1427-4221
    2300-2506
    Pojawia się w:
    Archives of Electrical Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Wooden composites from beech plywood and decorative veneers of different natural durability - their decay resistance and selected physico-mechanical properties
    Autorzy:
    Reinprecht, L.
    Izdinsky, J.
    Kmet'ova, L.
    Powiązania:
    https://bibliotekanauki.pl/articles/29893.pdf
    Data publikacji:
    2011
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    wooden composite
    beech plywood
    decorative veneer
    natural durability
    decay resistance
    physicomechanical property
    rotting fungi
    water resistance
    strength
    Opis:
    This work deals with decay resistance and selected physical and mechanical properties of wooden composites (WCs) prepared from 3.6 mm thick three-layer beech plywood and 0.6 mm thick decorative surface veneers of selected exotic (aningr´e, bubinga, iroko, khaya, padouk, sapelli, weng´e) and domestic (beech, European oak, sweet chestnut, walnut) wood species. Joining of veneers in the plywood and then also in the WCs was carried out by pressing processes using the PF glue Fenokol 43. The aim of the experiment was to determine the influence of surface veneers of different natural durability on rotting of the WCs, and on resistance of the WCs to water and mechanical loadings, as well. Decay resistance of individual veneers and WCs was tested by modified EN 113 against the brown-rot fungi Serpula lacrymans or Coniophora puteana, and the white-rot fungi Phanerochaete chrysosporium or Trametes versicolor. Weight losses of individual types of veneers and WCs caused by wood-destroying fungi were compared with weight losses of beech-veneer and beech-WC, respectively. The lowest weight losses at rotting processes showed the padouk-WC, i.e. WC prepared from the beech plywood and two the most durable padouk surface veneers. Density, water soaking, water swelling, tensile strength perpendicularly to the plane (?), and bending characteristics (MOR, MOE) of all WCs were determined in accordance with European standards. These physical and mechanical properties of the WCs were only partly influenced by the type of surface veneers. Selected types of the WCs, e.g. padouk-WC, could also be convenient for exterior expositions out of ground contact.
    Źródło:
    Folia Forestalia Polonica. Series B - Drzewnictwo; 2011, 42
    0071-6685
    Pojawia się w:
    Folia Forestalia Polonica. Series B - Drzewnictwo
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Interpolated-DFT-Based Fast and Accurate Amplitude and Phase Estimation for the Control of Power
    Autorzy:
    Borkowski, J.
    Kania, D.
    Powiązania:
    https://bibliotekanauki.pl/articles/221570.pdf
    Data publikacji:
    2016
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    control of power
    grid signal
    amplitude and phase estimation
    renewable energy
    interpolated DFT
    maximum decay side-lobes windows
    Opis:
    Quality of energy produced in renewable energy systems has to be at the high level specified by respective standards and directives. One of the most important factors affecting quality is the estimation accuracy of grid signal parameters. This paper presents a method of a very fast and accurate amplitude and phase grid signal estimation using the Fast Fourier Transform procedure and maximum decay side-lobes windows. The most important features of the method are elimination of the impact associated with the conjugate’s component on the results and its straightforward implementation. Moreover, the measurement time is very short ‒ even far less than one period of the grid signal. The influence of harmonics on the results is reduced by using a bandpass pre-filter. Even using a 40 dB FIR pre-filter for the grid signal with THD ≈ 38%, SNR ≈ 53 dB and a 20‒30% slow decay exponential drift the maximum estimation errors in a real-time DSP system for 512 samples are approximately 1% for the amplitude and approximately 8.5・10‒2 rad for the phase, respectively. The errors are smaller by several orders of magnitude with using more accurate pre-filters.
    Źródło:
    Metrology and Measurement Systems; 2016, 23, 1; 13-26
    0860-8229
    Pojawia się w:
    Metrology and Measurement Systems
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Description and Verification of the Contaminat Transport Models in Groundwater : Theory and Practice
    Opis i weryfikacja modeli transportu zanieczyszczeń w wodzie gruntowej : teoria i praktyka
    Autorzy:
    Aniszewski, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/204622.pdf
    Data publikacji:
    2013
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    advection
    dispersion
    non-linear adsorption
    biodegradation
    biological denitrification
    radioactive decay
    numerical calculations
    groundwater
    transport model
    adwekcja
    dyspersja
    adsorpcja nieliniowa
    biodegradacja
    denitryfikacja biologiczna
    rozpad promieniotwórczy
    obliczenia numeryczne
    wody podziemne
    model transportu
    Opis:
    This paper presents a general overview of 2D mathematical models for both the inorganic and the organic contaminants moving in an aquifer, taking into consideration the most important processes that occur in the ground. These processes affect, to a different extent, the concentration reduction values for the contaminants moving in a groundwater. In this analysis, the following processes have been taken into consideration: reversible physical non-linear adsorption, chemical and biological reactions (as biodegradation/biological denitrification) and radioactive decay (for moving radionuclides). Based on these 2D contaminant transport models it has been possible to calculate numerically the dimensionless concentration values with and without all the chosen processes in relation to both the chosen natural site (piezometers) and the chosen contaminants.In this paper, it has also been possible to compare all the numerically calculated concentration values to the measured concentration ones (in the chosen earlier piezometers) in relation to both the new unpublished measurement series of May 1982 and the new set of parameters used in these 2D contaminant transport models (as practical verification of these models).
    W artykule przedstawia się generalny przegląd 2D matematycznych modeli zarówno nieorganicznych, jak i organicznych zanieczyszczeń płynących w warstwie wodonośnej, biorąc pod uwagę najważniejsze procesy, jakie zachodzą w gruncie. Procesy te wpływają w różnym stopniu na wartości redukcji stężeń dla płynących w wodzie gruntowej zanieczyszczeń. W tej analizie wzięto pod uwagę następujące procesy: odwracalna nieliniowa fi zyczna adsorpcja, chemiczne i biologiczne reakcje (jako biodegradacja/biologiczna denitryfi kacja) oraz rozpad promieniotwórczy (dla płynących radionuklidów). W oparciu o prezentowane 2D modele transportu zanieczyszczeń było możliwe przeprowadzenie numerycznych obliczeń bezwymiarowych wartości stężeń z uwzględnieniem i bez uwzględnienia wszystkich wybranych procesów w odniesieniu zarówno do wybranego naturalnego gruntu (piezometrów) jak i do wybranych zanieczyszczeń. W pracy było również możliwe porównanie wszystkich obliczonych numerycznie wartości stężeń do wartości pomierzonych (w wybranych wcześniej piezometrach) w odniesieniu zarówno do nowej niepublikowanej wcześniej serii pomiarowej z maja 1982 jak i do nowego zestawu parametrów wykorzystanego w tych 2D modelach transportu zanieczyszczeń (jako praktyczna weryfi kacja tych modeli).
    Źródło:
    Archives of Environmental Protection; 2013, 39, 3; 3-21
    2083-4772
    2083-4810
    Pojawia się w:
    Archives of Environmental Protection
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Perceptually Correlated Parameters of Musical Instrument Tones
    Autorzy:
    Beauchamp, J. W.
    Powiązania:
    https://bibliotekanauki.pl/articles/177352.pdf
    Data publikacji:
    2011
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    musical timbre
    music synthesis
    loudness
    pitch
    duration
    attack
    decay
    spectral envelope
    spectral centroid
    spectral irregularity
    spectral flux
    vibrato
    inharmonicity
    discrimination
    dissimilarity relation
    multidimensional scaling (MDS)
    timbre transposition
    rms amplitude
    fundamental frequency
    correspondence
    Opis:
    In Western music culture instruments have been developed according to unique instrument acoustical features based on types of excitation, resonance, and radiation. These include the woodwind, brass, bowed and plucked string, and percussion families of instruments. On the other hand, instrument performance depends on musical training, and music listening depends on perception of instrument output. Since musical signals are easier to understand in the frequency domain than the time domain, much effort has been made to perform spectral analysis and extract salient parameters, such as spectral centroids, in order to create simplified synthesis models for musical instrument sound synthesis. Moreover, perceptual tests have been made to determine the relative importance of various parameters, such as spectral centroid variation, spectral incoherence, and spectral irregularity. It turns out that the importance of particular parameters depends on both their strengths within musical sounds as well as the robustness of their effect on perception. Methods that the author and his colleagues have used to explore timbre perception are: 1) discrimination of parameter reduction or elimination; 2) dissimilarity judgments together with multidimensional scaling; 3) informal listening to sound morphing examples. This paper discusses ramifications of this work for sound synthesis and timbre transposition.
    Źródło:
    Archives of Acoustics; 2011, 36, 2; 225-238
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-12 z 12

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