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    Wyświetlanie 1-10 z 10
    Tytuł:
    Laser frequency stability estimation and velocity measurement in the atmosphere with self-heterodyne
    Autorzy:
    Zhang, H.
    Wang, H.
    Zhao, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/174066.pdf
    Data publikacji:
    2016
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    frequency stability
    atmospheric propagation
    self-heterodyne
    Doppler velocity
    Opis:
    We present a novel method of self-heterodyne for laser frequency stability estimation in the atmosphere. At the same time, it is used in the Doppler velocity measurement for moving targets in the atmosphere. The transmission range is 16.2 km (round-trip propagation with 8.1 km) in the horizontal atmospheric path, and the measuring results showed that the frequency stability of the whole laser detection system is 53.4 kHz with 20.7 kHz stand deviation. This frequency stability is the integrated influence with the whole detection system not just for the laser, but it can be considered as the estimation of the laser’s frequency stability. It is much more practical for the heterodyne detection in the atmosphere. At last, the method of self-heterodyne was used for 16.2 km round trip velocity measurement. It is showed that the velocity absolute error is less than 1.5 cm/s in the turbulent atmosphere, and the relative error is not higher than 5%.
    Źródło:
    Optica Applicata; 2016, 46, 2; 305-316
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Error reduction of the Doppler lidar signal using a re-normalization method
    Autorzy:
    Park, N G
    Baik, S H
    Park, S K
    Kim, D L
    Kim, D. H.
    Powiązania:
    https://bibliotekanauki.pl/articles/173914.pdf
    Data publikacji:
    2014
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    injection-seeded laser
    Doppler lidar
    frequency locking
    wind lidar
    Doppler velocity measurement
    Opis:
    In this paper, we present a re-normalization method for a Doppler signal of a Doppler lidar system. For the Doppler lidar system, we used an injection-seeded pulsed Nd:YAG laser as a transmitter and an iodine cell as a Doppler frequency discriminator. A frequency locking system that uses the absorption feature of iodine gas is too sensitive to the external or internal noises (iodine cell temperature instability, laser frequency fluctuation, environmental noises, etc.) to maintain its locking point ideally, and this frequency locking error makes the Doppler lidar system acquire the noises as the Doppler frequency shifts. To reduce the Doppler signal error induced by a frequency locking error, we used a re-normalization method by an addition of a laser beam path separated from a transmitter to the Doppler frequency discriminator for re-normalization. In this method, fluctuations of the Doppler signal were reduced using the reference signal. The reduced amount of standard deviation between the Doppler signal and the re-normalization signal was 4.838×10–3 and the Doppler signals showed a 53.3% fluctuation reduction of the averaged error value by this method.
    Źródło:
    Optica Applicata; 2014, 44, 1; 103-111
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    SLAM – Based Approach to Dynamic Ship Positioning
    Autorzy:
    Wróbel, K. A.
    Powiązania:
    https://bibliotekanauki.pl/articles/116689.pdf
    Data publikacji:
    2014
    Wydawca:
    Uniwersytet Morski w Gdyni. Wydział Nawigacyjny
    Tematy:
    Dynamic Ship Positioning
    Simultaneous Localization and Mapping (SLAM)
    Dynamic Positioning (DP)
    Reference System
    SLAM Method
    SLAM Post-Processing
    Doppler Velocity Log (DVL)
    Hydroacoustics
    Opis:
    Dynamically positioned vessels, used by offshore industry, use not only satellite navigation but also different positioning systems, often referred to as ‘reference’ systems. Most of them use multiple technical devices located outside the vessel which creates some problems with their accessibility and performance. In this paper, a basic concept of reference system independent from any external device is presented, basing on hydroacoustics and Simultaneous Localization and Mapping (SLAM) method. Theoretical analysis of its operability is also performed.
    Źródło:
    TransNav : International Journal on Marine Navigation and Safety of Sea Transportation; 2014, 8, 1; 21-25
    2083-6473
    2083-6481
    Pojawia się w:
    TransNav : International Journal on Marine Navigation and Safety of Sea Transportation
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Non-invasive Ultrasound Doppler Effect Based Method of Liquid Flow Velocity Estimation in Pipe
    Autorzy:
    Biernacki, Paweł
    Gmyrek, Stanisław
    Magiera, Władysław
    Powiązania:
    https://bibliotekanauki.pl/articles/31339925.pdf
    Data publikacji:
    2023
    Wydawca:
    Polska Akademia Nauk. Czasopisma i Monografie PAN
    Tematy:
    information fusion
    flow velocity
    Doppler effecT
    Opis:
    This paper discusses the estimation of flow velocity from a multi-sensor scenario. Different estimation methods were used, which allow the effective measurement of the actual Doppler shift in a noisy environment, such as water with air bubbles, and on this basis the estimation of the flow velocity in the pipe was calculated. Information fusion is proposed for the estimates collected. The proposed approach focuses on the density of the fluid. The proposed method is capable of determining the flow velocity with high accuracy and small variations. Simulation results for plastic and steel (both galvanized and non-galvanized) pipes show the possibility of accurate fluid flow measurements without the need for sensors inside the pipe.
    Źródło:
    Archives of Acoustics; 2023, 48, 1; 141-148
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Comparative analysis of the vibrations of a different kind of engine mounted in the same new motor vehicles
    Autorzy:
    Sitnik, L.
    Magdziak-Tokłowicz, M.
    Wróbel, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/247090.pdf
    Data publikacji:
    2011
    Wydawca:
    Instytut Techniczny Wojsk Lotniczych
    Tematy:
    laser Doppler vibrometry
    engine vibration
    vibration velocity
    Opis:
    The paper presents the results of tests carried out on two spark-ignition engines: 1.4BZ 90CV CD and 1.4BZ 120CV CD installed in new Fiat Bravo (model 198, version 54A) motor cars. The latter engine model (120CV) was equipped with a supercharging system. The research consisted in comparing engine vibrations measured in specific and representative points. In order to determine the vertical component vibrations, the measurements were performed via a mirror. A PSV-400 laser Doppler vibrometer made by Polytec was used to measure vibration velocities. The vibrometric system directly measures two quantities: displacement and velocity. In the investigated case, vibration velocity is the variable which supplies better diagnostic information. Vibrations were measured for the car standing on its wheels and for the car jacked up to reduce the influence of the car vibration damping systems on the measurement results. The latter are presented in the form of comparative diagrams. Moreover, the fast Fourier transform was used to determine the frequency distribution. Prior to that signal was subjected to conditioning operations using parametric windowing and filtering. Interesting conclusions emerge from the obtained results and on their basis the effect of the drive unit on the behaviour of the car body can be assessed for different engine types and rotational speeds. It is shown that the way in which the engine is mounted affects the vibrations of the car.
    Źródło:
    Journal of KONES; 2011, 18, 4; 443-448
    1231-4005
    2354-0133
    Pojawia się w:
    Journal of KONES
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Velocity Field Characteristics at the Inlet to a Pipe Culvert
    Autorzy:
    Kolerski, T.
    Wielgat, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/241162.pdf
    Data publikacji:
    2014
    Wydawca:
    Polska Akademia Nauk. Instytut Budownictwa Wodnego PAN
    Tematy:
    Culvert
    Acoustic Doppler Velocitymeter
    velocity field
    turbulence
    Opis:
    A poorly designed culvert inlet structure causes scouring, which can lead to the collapse of the culvert and significant damage to the neighboring land. A set of laboratory tests was evaluated to examine velocity distribution at the culvert inlet. A three-dimensional acoustic Doppler velocimeter was used to measure instantaneous flow velocity upstream of the culvert. The analysis of mean velocities, turbulence strength, and Reynolds stresses was performed to understand the flow structure near the culvert entrance.
    Źródło:
    Archives of Hydro-Engineering and Environmental Mechanics; 2014, 61, 3-4; 127--140
    1231-3726
    Pojawia się w:
    Archives of Hydro-Engineering and Environmental Mechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    An Integrated Approach of Profi le Studies for Surface Water Velocity on a Steep Slope in a Rectangular Channel
    Autorzy:
    Ayalew, Abebe Temesgen
    Koshuma, Abera Ermias
    Ayele, Mesfi n Amaru
    Dirate, Democracy Dilla
    Powiązania:
    https://bibliotekanauki.pl/articles/2181750.pdf
    Data publikacji:
    2022
    Wydawca:
    Stowarzyszenie Inżynierów i Techników Mechaników Polskich
    Tematy:
    fluid mechanics
    velocity profiles
    rectangular channel
    Pitot tube
    Acoustic Doppler Velocitymeter
    ADV
    Opis:
    The flow velocity of water and its accurate surface profile estimation is important parameter as changes in climate increases the uneven rainfall patterns causing flood in downstream. It is important to know the velocity profile in steep open channel flows for solving the soil erosion, flooding and sediment transport problems in rivers or streams on steep slopes. A fixed bed laboratory experiment for a rectangular channel with steep slope is conducted to find the velocity profiles and surface profiles at different sections. Velocity profiles are presented at different sections in rectangular channel with steep slope. The outcome of the laboratory based experimental investigation shows that the velocity and surface profiles are influenced by the depth of flow of water and channel bed slope respectively.
    Źródło:
    Advances in Science and Technology. Research Journal; 2022, 16, 2; 74--80
    2299-8624
    Pojawia się w:
    Advances in Science and Technology. Research Journal
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Validation of a flow channel to investigate velocity profiles of friction-reducing ship coatings
    Autorzy:
    Weisheit, J.
    Schneider, V. E.
    Serr, J. M.
    Hagemeister, N.
    Oeffner, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/1841545.pdf
    Data publikacji:
    2021
    Wydawca:
    Uniwersytet Morski w Gdyni. Wydział Nawigacyjny
    Tematy:
    ship coatings
    flow Channel
    vessel velocity
    laser Doppler velocimeter
    computational fluid dynamics
    AIRCOAT project
    reynolds averaged navier stokes
    measurement volume
    Opis:
    Reducing friction with specialised hull coatings or air lubrication technologies has a potential reducing energy consumption and emissions in shipping. The EU project AIRCOAT combines both by developing a passive air lubrication technology inspired by nature that is implemented on a self-adhesive foil system. Besides validating the friction reduction it is of high interest to understand the underlying mechanism that causes the reduction. Therefore, a flow channel was designed, that creates a stationary turbulent flow within a square duct allowing for non-invasive measurements by laser doppler velocimetry. The high spatial resolution of the laser device makes recording velocity profiles within the boundary layer down to the viscous sublayer possible. Determination of the wall shear stress τ enables direct comparison of different friction reduction experiments. In this paper we validate the methodology by determining the velocity profile of the flat channel wall (without coatings). We further use the results to validate a CFD model in created in OpenFOAM. We find that velocities along the longitudinal axis are generally in good agreement between numerical and experimental investigations.
    Źródło:
    TransNav : International Journal on Marine Navigation and Safety of Sea Transportation; 2021, 15, 1; 225-231
    2083-6473
    2083-6481
    Pojawia się w:
    TransNav : International Journal on Marine Navigation and Safety of Sea Transportation
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Pumping capacity of pitched blade multi – stage impellers
    Autorzy:
    Jirout, T.
    Powiązania:
    https://bibliotekanauki.pl/articles/185756.pdf
    Data publikacji:
    2014
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    pitched blade impeller
    multi-stage impeller
    impeller pumping capacity
    velocity
    profile
    laser Doppler anemometry
    wirnik wielostopniowy
    wydajność pompowania wirnika
    prędkość
    profil
    laser Dopplera
    Opis:
    This paper extends knowledge about flow in an agitated batch with pitched blade multi-stage impellers. Effects of various geometrical parameters (blade number, distance between impellers) of pitched blade multi-stage impellers on pumping ability have been investigated. Axial velocity profiles were measured by LDA (Laser Doppler Anemometry). Axial pumping capacities were obtained by integration of measured axial velocity profiles in outflow from impellers. Main attention was focused on the effect of the distance between impellers in multi-stage configurations, on their pumping capacity and flow in the mixing bath in comparison with an independently operating pitched blade impeller with the same geometry. In case of a relatively close distance between Impellers H3/d= 0.5 - 0.75, the multi-stage impeller creates only one circulation loop and the impellers itself behave identically as pumps in series. However for relative higher distance of impellers than H3/d= 1.25, the multi-stage impeller creates two separated circulation loops.
    Źródło:
    Chemical and Process Engineering; 2014, 35, 1; 47-53
    0208-6425
    2300-1925
    Pojawia się w:
    Chemical and Process Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Visualization and flow velocity determination of molten polymers
    Wizualizacja oraz pomiar prędkości przepływu stopionych polimerów
    Autorzy:
    Sterzyński, Tomasz
    Bula, Karol
    Powiązania:
    https://bibliotekanauki.pl/articles/945818.pdf
    Data publikacji:
    2019
    Wydawca:
    Sieć Badawcza Łukasiewicz - Instytut Chemii Przemysłowej
    Tematy:
    molten polymer flow
    velocity
    non-direct methods
    Laser Doppler Velocimetry
    flow markers
    stopiony polimer
    przepływ
    metody pośrednie
    laserowa ocena przepływu z wykorzystaniem efektu Dopplera w optyce (LDV)
    markery przepływu
    Opis:
    The determination of flow vectors of molten polymer by dies and mold cavities filling is a topic of many investigations, realized by various measurement techniques. The non-direct measurements are based on temperature or pressure fields determination along the flow channels, where the sensors are usually positioned in the streaming polymers, leading to flow field disturbance. The Laser Doppler Velocimetry (LDV) is an efficient touchless measurement technique of streaming gases and liquids velocity, delivering directly values of the flow velocity and its direction. Principle and examples of LDV determined flow velocity distribution, are presented. The direct flow lines determination maybe done by using markers with a plate-like form, scanning electron microscopy (SEM) observation of fractured product surface.
    Pomiar wektorów prędkości przepływu stopionych polimerów przez dysze i kanały form wtryskowych stanowi przedmiot badań prowadzonych z zastosowaniem różnych technik. Pośrednie pomiary są oparte na ocenie pola wartości temperatury lub/i ciśnienia na długości kanału, przy czym czujniki z reguły są umieszczane bezpośrednio w przepływającym polimerze, co może prowadzić do zakłóceń przepływu. Laserowa ocena przepływu z wykorzystaniem efektu Dopplera w optyce (LDV) to bardzo efektywna bezstykowa metoda pomiaru przepływu gazów i cieczy, pozwalająca na określenie prędkości i kierunku przepływu. Opisano zasady dokonywania pomiarów oraz przykłady zastosowania LDV. Bezpośrednią ocenę charakteru przepływu umożliwia wykorzystanie markerów w postaci napełniaczy płytkowych w polimerze i następnie obserwacja przełomów wyrobu za pomocą skaningowej mikroskopii elektronowej (SEM).
    Źródło:
    Polimery; 2019, 64, 9; 569-576
    0032-2725
    Pojawia się w:
    Polimery
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
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