Wyniki wyszukiwania - BazTech

1

Waves, currents and seabed level change in the Port of Gdynia during extreme events

Sapiega P., Zalewska T., Wochna A.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2023

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Vol. 17 No. 3

515--521

EN

The primary purpose of the paper is to identify port areas most exposed to extreme hydrodynamic conditions (waves, sea currents, seabed level change). The results of modelling using SWAN wave model, MIKE 3D model, and reanalysis and measurement data were used in paper. Swell may exceed 0.8 m for winds exceeding 15 m s-1 from the west and south. During extreme conditions, sea currents can reach 0.4 ms-1 in the outer part of the bay adjacent to the port. Port basins do not show changes in the thickness of the seabed for the given maximum values of bottom currents. The most extensive deposition of the seabed and shore sediments (up to 0.04 m) is found on the Gdynia-Oksywie beach adjacent to the port and the approach fairway at the offshore currents. The outer area of the main breakwater is the most exposed to erosive activity (-0.012 m).

2

Aggregating sea surface hydrodynamic forecasts from multi-models for European seas

Frishfelds V., She J., Murawski J., Nielsen J. W.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2023

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Vol. 17 No. 3

533--541

EN

Maritime information services supporting European agencies such as the FRONTEX require European‐wide forecast solutions. Following a consistent approach, regional and global forecasts of the sea surface conditions from Copernicus Marine Service and national met‐ocean services are aggregated in space and time to provide a European‐wide forecast service on a common grid for the assistance of Search and Rescue operations. The best regional oceanographic model solutions are selected in regional seas with seamless transition to the global products covering the Atlantic Ocean. The regional forecast models cover the Black Sea, Mediterranean Sea, Baltic Sea, North Sea and combine the North Sea – Baltic Sea at the Danish straits. Two global models have been added to cover the entire model domain, including the regional models. The aggregated product is required to have an update frequency of 4 times a day and a forecasting range of 7 days, which most of the regional models do not provide. Therefore, smooth transition in time, from the shorter timerange, regional forecast models to the global model with longer forecast range are applied. The set of parameter required for Search and Rescue operations include sea surface temperature and currents, waves and winds. The current version of the aggregation method was developed for surface temperature and surface currents but it will be extended to waves in latter stages. The method relies on the calculation of aggregation weights for individual models. For sea surface temperature (SST), near real‐time satellite data at clear‐sky locations for the past days is used to determine the aggregation weights of individual forecast models. A more complicated method is to use a weighted multi‐model ensemble (MME) approach based on best forecast features of individual models and possibly including near real time observations. The developed method explores how satellite observations can be used to assess spatially varying, near real time weights of different forecasts. The results showed that, although a MME based on multiple forecasts only may improve the forecast, if the forecasts are unbiased, it is essential to use observations in the MME approach so that proper weights from different models can be calculated and forecast bias can be corrected. It is also noted that, in some months, e.g., June in Baltic Sea, even SST was assimilated, the forecast still show quite high error. There are also visible difference between different Copernicus Marine Environment Monitoring Service (CMEMS) satellite products, e.g. OSTIA and regional SST products, which can lead different forecast quality if different SST observation products are assimilated.

3

Pattern reconfigurable planar antenna array based on two circular defected ground structure

Ahmad Khalid Subhi, Aziz Mohamad Zoinol Abidin Abd.

Przegląd Elektrotechniczny

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2021

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R. 97, nr 7

52--55

EN

A pattern-reconfigurable dual-element microstrip antenna array based on reconfigurable two circular defected ground structures was proposed. Five switches are embedded in the two circular defected ground structures to tune the beam orientation. The proposed design able to work at two modes by selecting various combinations of the switch states. The proposed array was fabricated on a Roger board and prepared to shift the beam orientations at the working frequency of 7 GHz. Finally, one prototype of the antenna array was fabricated and tested. The simulated results illustrate that beam steered 52° while the measured beam steered 37°.

PL

Zaproponowano konfigurowalny dwuelementowy zestaw anten mikropaskowych oparty na rekonfigurowalnych dwóch kołowych strukturach naziemnych. Pięć przełączników jest osadzonych w dwóch okrągłych strukturach naziemnych z defektem, aby dostroić orientację wiązki. Proponowany projekt może pracować w dwóch trybach, wybierając różne kombinacje stanów przełącznika. Proponowany układ został wykonany na płycie Roger i przygotowany do zmiany orientacji wiązki przy częstotliwości roboczej 7 GHz. Wyprodukowano i przetestowano jeden prototyp układu antenowego. Symulowane wyniki pokazują, że wiązka kierowana była na 52 °, podczas gdy zmierzona wiązka na 37 °.

4

Frequency reconfigurable microstrip antenna array based on reconfigurable defected ground structure

Ahmad Khalid Subhi, Aziz Mohamad Zoinol Abidin Abd

Przegląd Elektrotechniczny

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2021

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R. 97, nr 8

114--120

EN

In this article, a frequency reconfigurable microstrip antenna array based on a defected ground structure is presented for C-band applications. The proposed antenna used the integration of two patches and the feeding network attached with a circular defected ground structure. The reconfigurable feature of the proposed antenna array is realized using a single switch inserted on the circular defected ground structure to modify the current distribution on the ground plane, which changes the resonance frequency. By switching the switch OFF, the antenna array eligible to resonate at two states and thus array centered at 4.83 and 5.36 GHz simultaneously. While switching ON, the antenna array eligible resonates at three states, and then the antenna array centered at 5, 5.52, and 5.90 GHz simultaneously. Furthermore, design steps, impedance bandwidth, and radiation patterns are introduced for the description and analysis of this antenna array. The finalized antenna array is simulated, manufactured, and measured successfully.

PL

W tym artykule przedstawiono układ anten mikropaskowych o rekonfigurowalnej częstotliwości, oparty na strukturze uszkodzonego uziemienia, do zastosowań w paśmie C. Proponowana antena wykorzystywała integrację dwóch łat i sieci zasilającej połączonej z kołową uszkodzoną strukturą uziemienia. Rekonfigurowalna cecha proponowanego szyku antenowego jest realizowana za pomocą pojedynczego przełącznika umieszczonego na kołowej uszkodzonej strukturze uziemienia w celu modyfikacji rozkładu prądu na płaszczyźnie uziemienia, co zmienia częstotliwość rezonansową. Po wyłączeniu przełącznika szyk antenowy kwalifikuje się do rezonansu w dwóch stanach, a zatem szyk jest wyśrodkowany jednocześnie na 4,83 i 5,36 GHz. Podczas włączania, szyk antenowy uprawniony do rezonowania w trzech stanach, a następnie szyk antenowy wyśrodkowany jednocześnie na 5, 5,52 i 5,90 GHz. Ponadto do opisu i analizy tego układu antenowego wprowadzono etapy projektowania, szerokość pasma impedancji i charakterystyki promieniowania. Gotowa szyka antenowa jest z powodzeniem symulowana, produkowana i mierzona.

5

Comparative analysis of the data on the surface currents and wind parameters generated by numerical models on the Szczecin Lagoon area

Kijewska M., Pleskacz K., Kasyk L.

TransNav : International Journal on Marine Navigation and Safety of Sea Transportation

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2018

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Vol. 12, no. 4

729--737

EN

This study focuses on the investigation of available surface currents and wind parameters for employing them in order to predict the survivor movement in the Szczecin Lagoon waters. For this purpose, the surface currents and wind parameters were generated by selected numerical models and the wind parameters were also measured with the telemetry devices. In this paper, the PM3D hydrodynamic model and the NEMS, ECMWF, GFS weather forecast models have been investigated. The measurements of the wind parameters, recorded at the Brama Torowa I and Trzebież stations, were also analyzed. As part of the research, an expert method was used to evaluate the surface currents parameters. In turn, the method based on comparing the forecasted wind parameters with the measured wind parameters was applied in order to assess uncertainties of these parameters. The comparative analyses of the data on the surface currents and wind parameters have been done and probabilistic models for uncertainties of these forecasted parameters have been formulated. Additionally, relations between the surface currents speeds and the wind speeds, in the case when their directions were consistent, have been also discovered.

6

Elastic electroconducting surface in magnetostatic field

Rudnicki M.

Journal of Theoretical and Applied Mechanics

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2005

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Vol. 43 nr 1

111--118

EN

The dynamical linear theory of a material surface placed in vacuum and subjected to an external strong magnetostatic field is considered. Motion of the surface is described by a position function The material of the surface is assumed to be an isotropic elastic non-magnetizable electric conductor. The residual stress is taken into account. Displacement-based field equations are obtained in coordinate-free notation.

PL

Przedmiotem rozważań jest teoria liniowa powierzchni materialnej umieszczonej w próżni i poddanej działaniu silnego zewnętrznego pola magnetostatycznego. Ruch powierzchni opisuje funkcja położenia. Założono, że materiał powierzchni jest izotropowy, sprężysty, niemagnetozywalny i przewodzący prąd elektryczny. Uwzględniono naprężenia rezydualne. Otrzymano równania rozwiązujące z użyciem przemieszczeń.