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Wyszukujesz frazę "Doppler system" wg kryterium: Temat


Tytuł:
Wind tunnel flux comparisons using a phase Doppler interferometer
Autorzy:
Roten, R.L.
Post, S.L.
Werner, A.
Safa, M.
Hewitt, A.J.
Tematy:
wind tunnel
flux measurement
Doppler interferometer
phase Doppler system
droplet
Pokaż więcej
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:
https://bibliotekanauki.pl/articles/65512.pdf  Link otwiera się w nowym oknie
Opis:
It is essential to know the movement of droplets in time and space (i.e. flux) when measuring and/or predicting spray drift in agricultural application. A study was performed to assess the flux measurements of a phase Doppler system against a standard monofilament system in a wind tunnel. The primary objectives of the study were to compare flux from a new phase Doppler system against 1.7 mm cotton and 2.0 mm nylon strings at varying wind speeds (1.4, 4.2, 8.3, 12.5, and 16.7 m ⋅ s–1) and spray exposures times (5, 10, 15, 30, and 60 s) with an overarching hypothesis that the active, phase Doppler is able to accurately measure the flux regardless of exposure and spray mass whereas the static string samplers are limited to a maximum retention. The phase Doppler did measure linearly as expected, however strings did not reach a point in which they loss mass; conversely, they appeared to overload with saturation. These findings are believed to be among many variables which influence the variability of previous mass balance studies.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Research and Medical Transcranial Doppler System
Autorzy:
Lewandowski, M.
Walczak, M.
Karwat, P.
Witek, B.
Karłowicz, P.
Tematy:
Doppler system
digital signal processing
hardware-software partitioning
field programmable gate array (FPGA)
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Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:
https://bibliotekanauki.pl/articles/177389.pdf  Link otwiera się w nowym oknie
Opis:
A new ultrasound digital transcranial Doppler system (digiTDS) is introduced. The digiTDS enables diagnosis of intracranial vessels which are rather difficult to penetrate for standard systems. The device can display a color map of flow velocities (in time-depth domain) and a spectrogram of a Doppler signal obtained at particular depth. The system offers a multigate processing which allows to display a numer of spectrograms simultaneously and to reconstruct a flow velocity profile. The digital signal processing in digiTDS is partitioned between hardware and software parts. The hardware part (based on FPGA) executes a signal demodulation and reduces data stream. The software part (PC) performs the Doppler processing and display tasks. The hardware-software partitioning allowed to build a flexible Doppler platform at a relatively low cost. The digiTDS design fulfills all necessary medical standards being a new useful tool in the transcranial field as well as in heart velocimetry research.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Modelowanie laserowego anemometru trójwiązkowego
Modeling of a Three Beam Laser Anemometer
Autorzy:
Wojtaszek, T.
Mroczka, J.
Tematy:
anemometria laserowa trójwiązkowa
modelowanie
rozproszenie światła
three beam phase Doppler system
light scattering
particle sizing
Pokaż więcej
Wydawca:
Stowarzyszenie Inżynierów i Techników Mechaników Polskich
Powiązania:
https://bibliotekanauki.pl/articles/157349.pdf  Link otwiera się w nowym oknie
Opis:
Niniejszy artykuł przedstawia model rozproszenia światła wykorzystywany do symulacji numerycznej właściwości i odpowiedzi trójwiązkowego laserowego anemometru dopplerowskiego, służącego do pomiaru parametrów fizycznych cząstek ośrodka dwufazowego. Przedstawiono porównanie cech objętości pomiarowej anemometru dwu i trójwiązkowego. Zaprezentowano odpowiedź: faza - wielkość i cząstki i częstotliwościową anemometru.
Model of ligt scattering of tree beam laser Doppler anemometer is presented. Its numerical and functional properties as well as response of the system are investigated. A comparision between measurements volume of three and two beam system is presented. Frequency response and pase shift vs. particle diameter diagrams are presented.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Analiza częstotliwościowa sygnału trójwiązkowego anemometru dopplerowskiego
Frequency analysis of a signal from three beam Doppler anemometer
Autorzy:
Wojtaszek, T.
Mroczka, J.
Tematy:
anemometria laserowa trójwiązkowa
modelowanie
rozproszenie światła
pomiar pozycji cząstki
pomiar trajektorii cząstki
tree beam phase Doppler system
light scattering
particle sizing
particle position
Pokaż więcej
Wydawca:
Stowarzyszenie Inżynierów i Techników Mechaników Polskich
Powiązania:
https://bibliotekanauki.pl/articles/152377.pdf  Link otwiera się w nowym oknie
Opis:
Niniejszy artykuł przedstawia ideę pomiaru położenia przemieszczającej się cząstki wzdłuż osi optycznej planarnego laserowego anemometru trójwiązkowego. Przedstawiona funkcja R pozwala określić z zadaną rozdzielczością połoenie badanej cząstki. Przedstawiono analityczną postać funkcji R będącej ilorazem amplitud prążków widma amplitudowego oraz dokonano prównania przypadku idealnego odwzorowania z przypadkiem rzeczywistym - wynikającym z prametrów wiązki oświetlającej.
The paper presents an idea of a position measurement of a particle moving along the optical axis of a tree beam planar laser Doppler anemometer. Position of a particle is determined with specified precision by te ratio R of frequency spectrum components. Analytical form of R and its properties are investigated. Comparision between an ideal form of R function and real - improved version are presented.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Errors of UAV autonomous landing system for different radio beacon configurations
Autorzy:
Kelner, J. M.
Ziółkowski, C.
Tematy:
aviation
Global Navigation Satellite System (GNSS)
autonomous landing system
unmanned aerial vehicle (UAV)
Doppler-based Landing System
drone
UAV drone
Doppler effect
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Wydawca:
Uniwersytet Morski w Gdyni. Wydział Nawigacyjny
Powiązania:
https://bibliotekanauki.pl/articles/117342.pdf  Link otwiera się w nowym oknie
Opis:
At the turn of the 20th and 21st centuries, development of microelectronics and microwave techniques allowed for minimization of electronic devices and systems, and the use of microwave frequency bands for modern radio communication systems. On the other hand, the global navigation satellite system (GNSS) have contributed to the popularization of radio navigation in civilian applications. These factors had a direct impact on the development and dissemination of unmanned aerial vehicles (UAVs). In the initial period, the UAVs were used mainly for the army needs. This results also from the legal aspects of the UAV use in the airspace. Currently, commercial UAVs for civilian applications, such as image recognition, monitoring, transport, etc., are presented increasingly. Generally, the GNSS system accuracy for the UAV positioning during a flight is enough. However, the GNSS use for automatic takeoff and landing may be insufficient. The extensive, ground-based navigation support systems used at airports by manned aircraft testify to these. In the UAV case, such systems are not used due to their complexity and price. For this reason, the novel dedicated take-off and landing systems are developed. The proposal of the autonomous landing system, which is based on the Doppler effect, was presented in 2017. In this case, the square-based beacon configuration was analyzed. This paper shows the influence of various beacon configurations in the Doppler-based landing system on the positioning error during the UAV landing approach.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Receiver of Doppler multistatic system for moving target detection and tracking
Autorzy:
Ostrowski, Z. J.
Tematy:
positioning system
Doppler shift
homodyne detection
Pokaż więcej
Wydawca:
Polskie Towarzystwo Akustyczne
Powiązania:
https://bibliotekanauki.pl/articles/332810.pdf  Link otwiera się w nowym oknie
Opis:
The article presents a method for solving major structural problems that occur in the receiver used in the multistatic Doppler system, aimed at determination of the trajectory and velocity of a moving target. In the system two transmitters emit acoustic continuous sinusoidal waves at different frequencies. The signals, scattered from a moving target are received by four hydrophones. Beside of the echoes, much larger signals coming directly from transmitters are recorded. It has been proved that in the presence of the direct high-amplitude signal, using currently available A/D converters, there is no possibility to detect the Doppler shift of small signals. The proposed approach is based on the homodyne frequency conversion of the received signals. Subsequently, the constant component and other unwanted products of the frequency conversion are filtered. The results of computer simulation have shown the effectiveness of the adopted design solution.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An influence of the covariance between single orbit parameters on the accuracy of observations of the pseudo-ranges and phase differences
Autorzy:
Skeivalas, Jonas
Paršeliūnas, Eimuntas
Putrimas, Raimundas
Šlikas, Dominykas
Tematy:
Global Positioning System
ephemeris
Doppler effect
dispersion
geodesy
Pokaż więcej
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:
https://bibliotekanauki.pl/articles/221830.pdf  Link otwiera się w nowym oknie
Opis:
The possibilities to improve values of the satellite orbit elements by employing the pseudo-ranges and differences of carrier phase frequencies measured at many reference GPS stations are analysed. An improvement of orbit ephemeris is achieved by solving an equation system of corrections of the pseudo-ranges and phase differences with the least-squares method. Also, equations of space coordinates of satellite orbit points expressed by ephemeris at fixed moments are used. The relation between the accuracy of the pseudo-ranges and phase differences and the accuracy of the satellite ephemeris is analysed. Formulae for estimation of the influence of the ephemeris on the measured pseudo-ranges and phase differences and for prediction of the accuracy of the pseudo-ranges and phase differences were obtained. An influence of the covariance between single orbit parameters on the accuracy of the pseudo-ranges and phase differences is detected.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A newborn with an alternative porto-caval shunt
Autorzy:
Damar, Çağrı
Gül Alımlı, Ayşe
Olgaç, Asburçe
Derinkuyu, Betül Emine
Özcan, Kudret Ebru
Koç, Ali Murat
Opis:
BACKGROUND: Absent ductus venosus (ADV) is a rare condition, but it should be known that this embryonic anomaly may be detected by fetal echocardiographic or newborn ultrasound examinations. CASE REPORT: We present a baby with an ADV and an accompanying alternative porto-caval shunt between the right portal vein and inferior vena cava detected on postnatal ultrasound examination. CONCLUSIONS: Variations in the fetal umbilical or porto-systemic circulations should be detected by fetal or newborn ultrasound examinations and kept in mind before common interventions such as UV catheterizations.
Dostawca treści:
Repozytorium Uniwersytetu Jagiellońskiego
Artykuł
Tytuł:
Ultrasonic Experimental Evaluation of the Numerical Model of the Internal Fluid Flow in the Kidney Cooling Jacket
Autorzy:
Gambin, Barbara
Korczak-Cegielska, Ilona
Secomski, Wojciech
Kruglenko, Eleonora
Nowicki, Andrzej
Tematy:
multi-canal system
fluid flow prediction
cooling jacket
flow Doppler measurement
Pokaż więcej
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Powiązania:
https://bibliotekanauki.pl/articles/31340112.pdf  Link otwiera się w nowym oknie
Opis:
Kidney Cooling Jacket (KCJ) preserves the kidney graft, wrapped in the jacket, against the too fast time of temperature rise during the operation of connecting a cooled transplant to the patient’s bloodstream. The efficiency of KCJ depends on the stationarity of the fluid flow and its spatial uniformity. In this paper, the fluid velocity field inside the three different KCJ prototypes has been measured using the 20 MHz ultrasonic Doppler flowmeter. The simplified 2D geometrical model of the prototypes has been presented using COMSOL-Multiphysics to simulate the fluid flow assuming the laminar flow model. By comparing the numerical results with experimental data, the simplified 2D model is shown to be accurate enough to predict the flow distribution of the internal fluid velocity field within the KCJ. The discrepancy between the average velocity measured using the 20 MHz Doppler and numerical results was mainly related to the sensitivity of the velocity measurements to a change of the direction of the local fluid flow stream. Flux direction and average velocity were additionally confirmed by using commercial colour Doppler imaging scanner. The current approach showed nearly 90% agreement of the experimental results and numerical simulations. It was important for justifying the use of numerical modelling in designing the baffles distribution (internal walls in the flow space) for obtaining the most spatially uniform field of flow velocity.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
S-band and Ku-band SAR system development for UAV-based applications
Autorzy:
Kaniewski, Piotr
Komorniczak, Wojciech
Leśnik, Czesław
Cyrek, Jacek
Susek, Waldemar
Serafin, Piotr
Łabowski, Michał
Tematy:
unmanned aerial vehicle
UAV
synthetic aperture radar
SAR
Range–Doppler algorithm
RDA
imagery intelligence system
IMINT system
Pokaż więcej
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Powiązania:
https://bibliotekanauki.pl/articles/221666.pdf  Link otwiera się w nowym oknie
Opis:
This paper describes a synthetic aperture radar system for tactical-level imagery intelligence installed on board an unmanned aerial vehicle. Selected results of its tests are provided. The system contains interchangeable S-band and Ku-band linear frequency-modulated, continuous wave radar sensors that were built within a frame of a research project named WATSAR, conducted by the Military University of Technology and WB Electronics S.A. One of several algorithms of radar image synthesis, implemented in the scope of the project, is described in this paper. The WATSAR system can create online and off-line radar images.
Dostawca treści:
Biblioteka Nauki
Artykuł

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