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    Wyświetlanie 1-9 z 9
    Tytuł:
    Variability of currents over the southern slope of the Gulf of Finland
    Autorzy:
    Suhhova, I.
    Pavelson, J.
    Lagemaa, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/48946.pdf
    Data publikacji:
    2015
    Wydawca:
    Polska Akademia Nauk. Instytut Oceanologii PAN
    Tematy:
    stratification
    upwelling
    downwelling
    Finland Gulf
    coastal sea water
    seasonal thermocline
    current velocity
    Źródło:
    Oceanologia; 2015, 57, 2
    0078-3234
    Pojawia się w:
    Oceanologia
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Phenotypic responses to water flow and wave exposure in aquatic plants
    Autorzy:
    Szmeja, J
    Galka, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/57001.pdf
    Data publikacji:
    2008
    Wydawca:
    Polskie Towarzystwo Botaniczne
    Tematy:
    water flow
    aquatic plant
    Polska
    river
    clonal growth
    wave exposure
    allocation
    botany
    current velocity
    phenotypic variation
    lake
    Opis:
    Plastic responses of 10 aquatic plant species from 5 rivers and 5 lakes in NW Poland were examined. Chara fragilis, C. delicatula, Potamogeton pectinatus, P. perfoliatus, P. natans, Spirodela polyrhiza, Hydrocharis morsus-ranae, Salvinia natans, Nymphoides peltata and Juncus bulbosus were the subject of research. In the running water of rivers, rhizophytes were generally bigger and they allocated from 0.6% to 58.6% more biomass for anchoring in the substrate than in stagnant water (ox bow lakes). In both flow variants rhizophytes allocated a similar biomass fraction for generative reproduction. On the other hand, under the influence of water flow pleustophytes reduced the mass of an individual (Spirodela by 25%, Hydrocharis 67%, Salvinia 77%) and emergent structures (p<0.001), and the number of sporangia (p<0.001). In both flow variants the input of biomass to generative reproduction was the same (Salvinia), or it was greater in running water (Hydrocharis; an increase from 4.9±1.3% to 15.1±3.6%). Under the conditions of strong wave action, in comparison with the lack of this environmental factor, Chara delicatula was several times shorter (p<0.001). However, it was also stouter, and as a result it had similar mass. In the areas of wave action the plant allocated 88.8% of its mass for anchoring in the substrate, whereas when there were no waves, only 22.7%.
    Źródło:
    Acta Societatis Botanicorum Poloniae; 2008, 77, 1
    0001-6977
    2083-9480
    Pojawia się w:
    Acta Societatis Botanicorum Poloniae
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Comparison of Time Warping Algorithms for Rail Vehicle Velocity Estimation in Low Speed Scenarios
    Autorzy:
    Hensel, S.
    Marinov, M. B.
    Powiązania:
    https://bibliotekanauki.pl/articles/221440.pdf
    Data publikacji:
    2017
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    velocity estimation
    cross-correlation
    dynamic programming
    eddy current sensors
    Opis:
    Precise measurement of rail vehicle velocities is an essential prerequisite for the implementation of modern train control systems and the improvement of transportation capacity and logistics. Novel eddy current sensor systems make it possible to estimate velocity by using cross-correlation techniques, which show a decline in precision in areas of high accelerations. This is due to signal distortions within the correlation interval. We propose to overcome these problems by employing algorithms from the field of dynamic programming. In this paper we evaluate the application of correlation optimized warping, an enhanced version of dynamic time warping algorithms, and compare it with the classical algorithm for estimating rail vehicle velocities in areas of high accelerations and decelerations.
    Źródło:
    Metrology and Measurement Systems; 2017, 24, 1; 161-173
    0860-8229
    Pojawia się w:
    Metrology and Measurement Systems
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Structure and local parameters of self-compressed plasma streams in external magnetic field
    Autorzy:
    Volkova, Yuliia
    Solyakov, Dmytro
    Marchenko, Anna
    Chebotarev, Volodymyr
    Garkusha, Igor
    Makhlai, Vadym
    Ladygina, Maryna
    Tetyana, Merenkova
    Yeliseyev, Dmytro
    Petrov, Yurii
    Staltsov, Valerii
    Powiązania:
    https://bibliotekanauki.pl/articles/2202565.pdf
    Data publikacji:
    2023
    Wydawca:
    Instytut Chemii i Techniki Jądrowej
    Tematy:
    current sheet
    electric probe
    electron temperature
    drift velocity
    pinching discharge
    plasma accelerators
    Opis:
    The influence of the external axial magnetic field on pinching plasma flows generated by a magnetoplasma compressor (MPC) has been studied using magnetic and electric probes. In the presence of an external magnetic field, temperature measurements show two groups of electrons with different temperatures near the plasma stream core. The external magnetic field leads to a noticeable increase in the electric current in the plasma stream, electron temperature, and the formation of the current-sheet-like structure observed in the MPC for the first time.
    Źródło:
    Nukleonika; 2023, 68, 1; 3--9
    0029-5922
    1508-5791
    Pojawia się w:
    Nukleonika
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Numerical study on two dimensional distribution of streamwise velocity in open channel turbulent flows with secondary current effect
    Autorzy:
    Mohan, S.
    Kundu, S.
    Ghoshal, K.
    Kumar, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/38616700.pdf
    Data publikacji:
    2021
    Wydawca:
    Instytut Podstawowych Problemów Techniki PAN
    Tematy:
    velocity distribution
    open channel flow
    turbulent flow
    RANS equations
    secondary current
    finite difference method
    Opis:
    For studying mechanism of sediment transport in river flows, open channel flow is a prototype. Flow has always three components of velocity for all types of channel geometry and for a time independent uniform flow along streamwise or main flow direction, all the components of velocity are functions of lateral and vertical coordinates. The present study investigates the two dimensional distribution of streamwise (or longitudinal) velocity starting from the Reynolds averaged Navier–Stokes equation for a turbulent open channel flow which is steady and uniform along the main flow direction. Secondary flows both along the vertically upward direction and along the lateral direction are considered which are also taken as functions of lateral and vertical coordinates. Inclusion of the secondary current brings the effect of dip phenomenon in the model. The resulting second order partial differential equation is solved numerically. The model is validated for all the cross-sectional, transverse and centreline velocity distribution by comparing with existing relevant set of experimental data and also with an existing model. Comparison results show good agreement with data as well as with the previous model proving the efficiency of the model. It is found that the transverse velocity distribution depends on the formation of circular vortex in the cross-sectional plane and becomes periodic as the number of circular vortex increases for increasing aspect ratios.
    Źródło:
    Archives of Mechanics; 2021, 73, 2; 175-200
    0373-2029
    Pojawia się w:
    Archives of Mechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Three-dimensional underwater path planning based on modified potential field algorithm in time-varying current
    Autorzy:
    Wang, Shasha
    Feng, Guilin
    Wang, Dan
    Tuo, Yulong
    Powiązania:
    https://bibliotekanauki.pl/articles/32917893.pdf
    Data publikacji:
    2023
    Wydawca:
    Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
    Tematy:
    AUV
    3D underwater path planning
    time-varying current
    modified artificial potential field
    velocity synthesis
    Opis:
    The article addresses the three-dimensional (3D) underwater path planning problem of an autonomous underwater vehicle (AUV) in a time-varying current. A modified artificial potential field algorithm combining the velocity vector synthesis method is proposed to search for the optimal path. The modified potential field (MPF) algorithm is designed to dynamically plan the non-collision path. Meanwhile, this modified method is also proved to be an effective solution to the goals not reachable with obstacles nearby (GNRON), U-shaped trap, and rotation unreachable problems. To offset the influence of time-varying current, the velocity synthesis approach is designed to adjust the AUV movement direction. Besides, considering path planning in the complex underwater environment, the multi-beam forward-looking sonar (FLS) model is used. Finally, simulation studies substantiate that the designed algorithm can implement the AUV path planning effectively and successfully in a 3D underwater environment.
    Źródło:
    Polish Maritime Research; 2023, 1; 33-42
    1233-2585
    Pojawia się w:
    Polish Maritime Research
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Current observations from a looking down vertical V-ADCP: interaction with winds and tide? The case of Giglio Island (Tyrrhenian Sea, Italy)
    Autorzy:
    Cutroneo, L.
    Ferretti, G.
    Scafidi, D.
    Ardizzone, G.D.
    Vagge, G.
    Capello, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/47976.pdf
    Data publikacji:
    2017
    Wydawca:
    Polska Akademia Nauk. Instytut Oceanologii PAN
    Tematy:
    wind
    tide
    interaction
    sea level
    normalized cross-correlation function
    wind velocity
    current measurement
    Giglio Island
    Tyrrhenian Sea
    Italy
    Opis:
    In the context of the environmental monitoring of the Concordia wreck removal project, measurements of currents, winds and sea level height were made along the eastern coast of the Giglio Island, Tyrrhenian Sea (Italy), during 2012—2013. The aim of the study was to investigate the effect of atmospheric forcing and periodic sea-level changes on the coastal currents. Normalised Cross-Correlation Function analysis allowed us to correlate these observations. A marked inter-seasonal variability was found in both current and local wind velocity observations but a significant level of correlation between the data was only found during strong wind events. Current and wind directions appeared to be uncorrelated and current measurements showed a predominant NW—SE direction, presumably linked to the shape and orientation of Giglio Island itself. During strong winds from the SSE, current flow was towards the NNW but it suddenly switched from the NNW to the SE at the end of wind events. The results show that, at Giglio Island, currents are principally dominated by the general cyclonic Tyrrhenian circulation, and, secondly, by strong wind events. The sea level had no effects on the current regime.
    Źródło:
    Oceanologia; 2017, 59, 2
    0078-3234
    Pojawia się w:
    Oceanologia
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Sediment transport beyond the surf zone under waves and currents of the non-tidal sea: Lubiatowo (Poland) case study
    Autorzy:
    Ostrowski, R.
    Stella, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/241109.pdf
    Data publikacji:
    2016
    Wydawca:
    Polska Akademia Nauk. Instytut Budownictwa Wodnego PAN
    Tematy:
    wave-induced nearbed oscillations
    sea currents
    wind-driven current
    sand grain diameter
    bed shear stress
    friction velocity
    sediment transport
    Opis:
    The paper deals with the sandy coastal zone at Lubiatowo in Poland (the south Baltic Sea). The study comprises experimental and theoretical investigations of hydrodynamic and lithodynamic processes in the coastal region located close to the seaward boundary of the surf zone and beyond the surf zone. The analysis is based on field data collected at the IBW PAN Coastal Research Station in Lubiatowo. The data consist of wind velocity reconstructed from the long-term wave climate, deep-water wave buoy records and sea bottom soil parameters. Nearbed flow velocities induced by waves and currents, as well as bed shear stresses are theoretically modelled for various conditions to determine sediment motion regimes in the considered area. The paper discusses the possibility of occasional intensive sediment transport and the occurrence of distinct sea bed changes at bigger water depths.
    Źródło:
    Archives of Hydro-Engineering and Environmental Mechanics; 2016, 63, 1; 63-77
    1231-3726
    Pojawia się w:
    Archives of Hydro-Engineering and Environmental Mechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Surrogate synthesis of excitation systems for frame tangential eddy current probes
    Autorzy:
    Halchenko, Volodymir Yakovych
    Trembovetska, Ruslana Volodymyrivna
    Tychkov, Volodymir Volodymyrovych
    Powiązania:
    https://bibliotekanauki.pl/articles/1955174.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    additive neural network regression
    eddy current probe
    stochastic optimization algorithm
    surrogate optimization
    uniform eddy current density distribution
    velocity effect
    addytywna regresja sieci neuronowej
    sonda prądów wirowych
    algorytm optymalizacji stochastycznej
    optymalizacja zastępcza
    równomierny rozkład gęstości prądów wirowych
    efekt prędkości
    Opis:
    Existing scientific studies devoted to the design of eddy-current probes with a priori given configuration of the electromagnetic excitation field, which provide a uniform eddy current density distribution, consider a wide class of such, but are limited to the case when the probe is stationary relative to the testing object. Therefore, the actual problem is the synthesis of moving tangential eddy current probes with a frame excitation system that provides a uniform eddy current density distribution in the testing object, the solution of which is proposed in this study. A mathematical method for nonlinear surrogate synthesis of excitation systems for frame moving tangential surface eddy current probes, which implements a uniform eddy current density distribution of the testing zone object, is proposed. A metamodel of the volumetric structure of the excitation system of the frame tangential eddy current probe, applied in the process of surrogate optimal parametric synthesis, has been created. The examples of nonlinear synthesis of excitation systems using modern metaheuristic stochastic algorithms for finding the global extremum are considered. The numerical results of the obtained solutions of the problems are presented. The efficiency of the synthesized structures of excitation systems in comparison with classical analogs is shown on the graphs of the eddy current density distribution on the object surface in the testing zone.
    Źródło:
    Archives of Electrical Engineering; 2021, 70, 4; 743-757
    1427-4221
    2300-2506
    Pojawia się w:
    Archives of Electrical Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-9 z 9

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