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Wyświetlanie 1-15 z 395
Tytuł:
Two-Phase Flow Measuring with Ultrasonic Tomography
Autorzy:
Qorbani, Omid
Aghdam, Esmaeil Najafi
Powiązania:
https://bibliotekanauki.pl/articles/176579.pdf
Data publikacji:
2020
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:
two-phase flowmeter
ultrasonic flowmeter
ultrasonic tomography
Opis:
The exact measurement of multiphase flow is an important and essential task in the oil and petrochemical related industries. Several methods have already been proposed in this field. In the existing methods, flow rate measurement depends on the fluid flow pattern. Flow pattern recognition requiring calibration has created instability in such systems. In this paper, a imple and reliable method is proposed which is based on ultrasonic tomography. It is free from calibration and instability problems that existing methods have. The obtained data from a 32-digit array of ultrasonic sensors have been used and the two-phase flow rate including liquid and gas phases have been calculated through a simple algebraic algorithm. Simulation results show that while applying this method the measurement technique is independent from the fluid flow pattern and the system error is decreased. For the proposed algorithm, the average amount of the spatial imaging error (SIE) for a bubble at different positions inside the pipe is about 5%.
Źródło:
Archives of Acoustics; 2020, 45, 3; 459-465
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Audio Feature Space Analysis for Emotion Recognition from Spoken Sentences
Autorzy:
Smietanka, Lukasz
Maka, Tomasz
Powiązania:
https://bibliotekanauki.pl/articles/1953467.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:
speech analysis
classification
emotional speech
Opis:
An analysis of low-level feature space for emotion recognition from the speech is presented. The main goal was to determine how the statistical properties computed from contours of low-level features influence the emotion recognition from speech signals. We have conducted several experiments to reduce and tune our initial feature set and to configure the classification stage. In the process of analysis of the audio feature space, we have employed the univariate feature selection using the chi-squared test. Then, in the first stage of classification, a default set of parameters was selected for every classifier. For the classifier that obtained the best results with the default settings, the hyperparameter tuning using cross-validation was exploited. In the result, we compared the classification results for two different languages to find out the difference between emotional states expressed in spoken sentences. The results show that from an initial feature set containing 3198 attributes we have obtained the dimensionality reduction about 80% using feature selection algorithm. The most dominant attributes selected at this stage based on the mel and bark frequency scales filterbanks with its variability described mainly by variance, median absolute deviation and standard and average deviations. Finally, the classification accuracy using tuned SVM classifier was equal to 72.5% and 88.27% for emotional spoken sentences in Polish and German languages, respectively.
Źródło:
Archives of Acoustics; 2021, 46, 2; 271-277
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The origin of fern Athyrium christensenianum (Koidz.) Seriz. (Athyriaceae)
Autorzy:
Hori, K.
Powiązania:
https://bibliotekanauki.pl/articles/2117857.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:
asteraceae
chromosome number
Europe
Hieracium
karyotype
Opis:
Chromosome numbers for 15 taxa of Hieracium s.lat. (including two taxa of Pilosella Vaill.) from Bosnia and Herzegovina, Bulgaria, Greece, North Macedonia, Poland, Romania and Slovakia are given and their metaphase plates are illustrated. Chromosome numbers are published for the first time for H. pannosum subsp. parnassi Nägeli & Peter from Greece (3x and 4x), and for an undescribed species of H. sect. cernua from North Macedonia (4x). a new, diploid chromosome number was found in H. bracteolatum s.lat. from Greece.
Źródło:
Acta Biologica Cracoviensia. Series Botanica; 2019, 61, 2
0001-5296
Pojawia się w:
Acta Biologica Cracoviensia. Series Botanica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Chromosome numbers in Hieracium (asteraceae) from Central and Southeastern Europe VII
Autorzy:
Musiał, K.
Szeląg, Z.
Powiązania:
https://bibliotekanauki.pl/articles/31341332.pdf
Data publikacji:
2023
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Źródło:
Acta Biologica Cracoviensia. Series Botanica; 2023, 65, 1; 23-28
0001-5296
Pojawia się w:
Acta Biologica Cracoviensia. Series Botanica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Algorithm for Computationally Efficient Imaging of Sound Speed in Conventional Ultrasound Sonography
Autorzy:
Karwat, Piotr
Powiązania:
https://bibliotekanauki.pl/articles/31339779.pdf
Data publikacji:
2023
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:
speed of sound
ultrasound imaging
computational complexity
Opis:
The speed of sound (SoS) in tissues reflects their mechanical properties and therefore can carry valuable diagnostic information. In conventional ultrasound sonography (US), however, this information is not readily available. Furthermore, since the actual SoS is unknown, image reconstruction is carried out using an average SoS value for soft tissues. The resulting local deviations from the actual SoS lead to aberrations in US images. Methods for SoS imaging in US therefore have the potential to enable the correction of aberrations in classical US. In addition, they could also become a new US modality. There are several approaches to SoS image reconstruction. They differ in terms of input data requirements, computational complexity, imaging quality, and the potential for signal analysis at the intermediate stages of processing. This article presents an algorithm with multi-stage processing and low computational complexity. The algorithm was verified through numerical simulations and phantom measurements. The obtained results show that it can correctly estimate SoS in layered media, which in most cases model the tissue structure well. With its computational complexity of O(n), the algorithm can be implemented in real-time ultrasound imaging systems with limited hardware performance, such as portable ultrasound devices.
Źródło:
Archives of Acoustics; 2023, 48, 4; 549-558
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Extended High Frequency Hearing Thresholds in Tinnitus Patients with Normal Hearing
Autorzy:
Ristovska, Lidija
Jachova, Zora
Powiązania:
https://bibliotekanauki.pl/articles/31339952.pdf
Data publikacji:
2022
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:
extended high frequency
hearing loss
tinnitus
Opis:
The aim of the study was to compare the extended high-frequency (EHF) hearing thresholds (10–16 kHz) in tinnitus and non-tinnitus ears, in a group of 98 patients with unilateral tinnitus and normal hearing at standard audiometric frequencies, in a 0.125–8 kHz range. It was found that a total of 65 patients (66%) had a hearing loss (a threshold shift >20 dB HL) in the EHF range and the EHF hearing loss occurred more frequently in the tinnitus ear than in the non-tinnitus ear. The data also indicate that the EHF thresholds increased with the patient’s age and were in most patients higher in the tinnitus ear than in the non-tinnitus ear.
Źródło:
Archives of Acoustics; 2022, 47, 4; 449-455
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Single Degree of Freedom Simulation Model of Underwater Explosion Impact
Autorzy:
Grządziela, Andrzej
Załęska-Fornal, Agata
Kluczyk, Marcin
Powiązania:
https://bibliotekanauki.pl/articles/176933.pdf
Data publikacji:
2020
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:
UNDEX
simulation
impact model
bubble
Opis:
The hulls of naval ships are exposed to forces and moments coming from internal and external sources. Usually, these are interactions that can be described mathematically by harmonic and polyharmonic functions. The shock of UNDEX type (underwater explosion) works completely differently and its time waveform is difficult to describe with mathematical functions as pressure vs. time. The paper presents a simplification of physical and mathematical models of 1-D kickoff pressure whose aim is performance the simulation of the external force of the detonation wave. The proposed models were verified and tuned on naval, sea trials. The main goals of the proposed models are to perform simulation calculations of the detonation pressure for different explosion charge weights from different distances of the UNDEX epicentre for the design process of machine foundation. The effects of pressure are transformed as impulses exposed on shock absorber mounted at light shock machine.
Źródło:
Archives of Acoustics; 2020, 45, 2; 341-348
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Repetitive Acoustic Streaming Patterns in Sinusoidal Shaped Microchannels
Autorzy:
Jannesar, Elnaz Attar
Hamzehpour, Hossein
Powiązania:
https://bibliotekanauki.pl/articles/177380.pdf
Data publikacji:
2020
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:
acoustic streaming
sinusoidal boundaries
microscale vortices
sub-microparticle trapping
Opis:
Geometry of the fluid container plays a key role in the shape of acoustic streaming patterns. Inadvertent vortices can be troublesome in some cases, but if treated properly, the problem turns into a very useful parameter in acoustic tweezing or micromixing applications. In this paper, the effects of sinusoidal boundaries of a microchannel on acoustic streaming patterns are studied. The results show that while top and bottom sinusoidal walls are vertically actuated at the resonance frequency of basic hypothetical rectangular microchannel, some repetitive acoustic streaming patterns are recognised in classifiable cases. Such patterns can never be produced in the rectangular geometry with flat boundaries. Relations between geometrical parameters and emerging acoustic streaming patterns lead us to propose formulas in order to predict more cases. Such results and formulations were not trivial at a glance.
Źródło:
Archives of Acoustics; 2020, 45, 1; 35-48
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Optimal Selection of Multicomponent Matching Layers for Piezoelectric Transducers using Genetic Algorithm
Autorzy:
Gudra, Tadeusz
Banasiak, Dariusz
Powiązania:
https://bibliotekanauki.pl/articles/1953531.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:
acoustic impedance
matching layers
ultrasonic transducers
Opis:
One major problem in the design of ultrasonic transducers results from a huge impedance mismatch between piezoelectric ceramics and the loading medium (e.g. gaseous, liquid, and biological media). Solving this problem requires the use of a matching layer (or layers). Optimal selection of materials functioning as matching layers for piezoelectric transducers used in transmitting and receiving ultrasound waves strictly depends on the type of the medium receiving the ultrasound energy. Several methods allow optimal selection of materials used as matching layers. When using a single matching layer, its impedance can be calculated on the basis of the Chebyshev, DeSilets or Souquet criteria. In the general case, the typically applied methods use an analogy to a transmission line in order to calculate the transmission coefficient T. This paper presents an extension of transmission coefficient calculations with additional regard to the attenuation coefficients of particular layers. The transmission coefficient T is optimised on the basis of a genetic algorithm method. The obtained results indicate a significant divergence between the classical calculation methods and the genetic algorithm method.
Źródło:
Archives of Acoustics; 2020, 45, 4; 699-707
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Radiation Impedance for Square Piston Sources on Infinite Circular Cylindrical Baffles
Autorzy:
Valacas, John L.
Powiązania:
https://bibliotekanauki.pl/articles/1953533.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:
cylindrical baffle
radiation impedance
radiation mass-load
piston source
Opis:
The evaluation of complex radiation impedance for a square piston source on an infinite circular-cylindrical baffle is associated to the Greenspon-Sherman formulation for which novel evaluation methods are proposed. Unlike existing methods results are produced in a very wide range of frequencies and source semi-angles with controllable precision. For this reason closed-form expressions are used to describe the truncation errors of all integrals and infinite sums involved. Impedance values of increased accuracy are also provided in tabulated form for engineering use and a new radiation mass-load model is derived for low-frequencies.
Źródło:
Archives of Acoustics; 2020, 45, 4; 663-679
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
About Unusual Diffraction and Thermal Self-Action of Magnetosonic Beam
Autorzy:
Perelomova, Anna
Powiązania:
https://bibliotekanauki.pl/articles/31340117.pdf
Data publikacji:
2022
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:
non-linear magnetoacoustics
diffraction of beams
acoustic thermal self-action
magnetohydrodynamics
Opis:
The dynamics of slightly diverging two-dimensional beams whose direction forms a constant angle θ with the equilibrium straight magnetic strength is considered. The approximate dispersion relations and corresponding links which specify hydrodynamic perturbations in confined beams are derived. The study is dedicated to the diffraction of a magnetosonic beam and nonlinear thermal self-action of a beam in a thermoconducting gaseous plasma. It is shown that the divergence of a beam and its thermal self-action is unusual in some particular cases of parallel propagation (θ = 0) and has no analogues in the dynamics of the Newtonian beams. The nonlinear attenuation of Newtonian beams leads to their defocusing in gases, whereas the unusual cases correspond to the focusing in a presence of magnetic field. The examples of numerical calculations of thermal self-action of magnetoacoustic beams with shock fronts are considered in the usual and unusual cases of diffraction concerning stationary and non-stationary self-action. It is discovered that the diffraction is more (θ = 0) or less (θ = π/2) manifested as compared to that of the Newtonian beams. The beams which propagate oblique to the magnetic field do not reveal diffraction. The special case, when the sound and Alfvénic speeds are equal, is discussed. This magnetosonic beams incorporate acoustic and Alfvénic properties and do not undergo diffraction in this particular case.
Źródło:
Archives of Acoustics; 2022, 47, 3; 355-362
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Sound Wave Radiation from Partially Lined Duct
Autorzy:
Tiryakioglu, Burhan
Demir, Ahmet
Powiązania:
https://bibliotekanauki.pl/articles/177899.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:
Wiener-Hopf
Fourier transform
duct
saddle point
Opis:
The radiation of sound waves from partially lined duct is treated by using the mode-matching method in conjunction with the Wiener-Hopf technique. The solution is obtained by modification of the Wiener-Hopf technique and involves an infinite series of unknowns which are determined from an infinite system of linear algebraic equations. Numerical solution of this system is obtained for various values of the problem parameters, whereby the effects of these parameters on the sound diffraction are studied. A perfect agreement is observed when the results of radiated field are compared numerically with a similar work existing in the literature.
Źródło:
Archives of Acoustics; 2019, 44, 2; 239-249
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Nonlinear Interaction of Magnetoacoustic Modes in a Quasi-Isentropic Plasma Flow
Autorzy:
Perelomova, Anna
Powiązania:
https://bibliotekanauki.pl/articles/1953454.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:
non-linear magnetohydrodynamics
adiabatical instability
Opis:
The nonlinear interaction of magnetoacoustic waves in a plasma is analytically studied. A plasma is an open system. It is affected by the straight constant equilibrium magnetic flux density forming constant angle with the wave vector which varies from 0 till π. The nonlinear instantaneous equation which describes excitation of secondary wave modes in the field of intense magnetoacoustic perturbations is derived by use of projecting. There is a diversity of nonlinear interactions of waves in view of variety of wave modes, which may be slow or fast and may propagate in different directions. The excitation is analysed in the physically meaningful cases, that is: harmonic and impulsive exciter, oppositely or accordingly directed dominant and secondary wave modes.
Źródło:
Archives of Acoustics; 2021, 46, 2; 323-333
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Acoustic Hysteresis in Flows with Different Kinds of Relaxation and Attenuation
Autorzy:
Perelomowa, Anna
Powiązania:
https://bibliotekanauki.pl/articles/31339946.pdf
Data publikacji:
2022
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:
relaxation
acoustic hysteresis
acoustical activity
Opis:
Graphs in the thermodynamic plane acoustic pressure versus excess acoustic density representing acoustic hysteresis, are considered as indicators of relaxation processes, equilibrium parameters of a flow, and kinds of wave exciters. Some flows with deviation from adiabaticity are examined: the Newtonian flow of a thermoconducting gas, the flow of a gas with vibrational relaxation, the flow of liquid electrolyte with a chemical reaction, and the Bingham plastic flow. The total range of characteristic frequencies of a harmonic exciter is taken into account. The impulsive sound is considered as well. The peculiarities of hysteretic behaviour are discussed in dependence with the kind and degree of deviation form adiabaticity. Examples of acoustically active flows are discussed.
Źródło:
Archives of Acoustics; 2022, 47, 4; 519-527
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 395

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