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Synchronization system for underwater acoustic communications using in shallow waters

Schmidt Jan H., Schmidt Aleksander M.

Vibrations in Physical Systems

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2023

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Vol. 34, nr 1

art. no. 2023102

EN

A reliable synchronization system of the transmitted data frame has a significant impact on the efficiency of the underwater communication system. This applies in particular to communication systems dedicated to work in shallow waters, where the phenomenon of multipath permanently occurs. To overcome these difficulties, the concept of a synchronization system consisting of two broadband signals of opposite monotonicity was presented. The method of receiving these signals has been described in detail. The stochastic channel model with Rician fading and the Watermark simulator was used to test the efficiency of the synchronization system in the underwater multipath channel.

2

Underwater acoustic communication system using broadband signal with hyperbolically modulated frequency

Schmidt Jan H., Schmidt Aleksander M.

Vibrations in Physical Systems

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2021

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Vol. 32, nr 1

art. no. 2021116

EN

The implementation of reliable acoustic underwater communication in shallow waters is a scientific and engineering challenge, mainly due to the permanent occurrence of the multipath phenomenon. The article presents the concept of a transmission system using a broadband signal with hyperbolically modulated frequency (HFM) to transmit data symbols and synchronize data frames. The simulation tests were carried out in channels with Rician fading, reflecting the short- and medium-range shallow water channels. The simulation also took into account the presence of additive Gaussian noise in the channel on the functioning of the receiver. The obtained results prove the high reliability of the underwater communication system based on broadband HFM signals.

3

Regressive-transgressive cyclothem with facies record of the re-flooding window in the Late Silurian carbonate succession (Podolia, Ukraine)

Łuczyński P., Kozłowski W., Skompski S.

Acta Geologica Polonica

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2015

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Vol. 65, no. 3

297--318

EN

The term “re-flooding window” was recently proposed as a time-interval connected with the transgressive stage of present day peri-reefal development. In the analysis presented here, a fossil record of a re-flooding window has been recognized. Nine Late Silurian carbonate sections exposed on the banks of the Dnister River in Podolia (Ukraine) have been correlated base on bed-by-bed microfacies analysis and spectral gamma ray (SGR) measurements. Correlated were sections representing settings ranging from the inner part of a shallow-water carbonate platform to its slope, through an organic buildup. The reconstructed depositional scenario has been divided into six development stages, with the first three representing a regressive interval and the latter three a transgressive interval of the basin’s history. The re-flooding window has been identified at the beginning of a transgressive part of the succession. Surprisingly, it is characterized by an extremely fast growth of a shallow, tide-dominated platform and by deposition of calciturbiditic layers in a more basinal area. The interpreted succession is a small-scale model illustrating the reaction of carbonate depositional sub-environments to sea level changes and determining the facies position of the stromatoporoid buildups within the facies pattern on a Silurian shelf. The use of SGR analyses in shallow water, partly high-energy, carbonate facies, both for correlation purposes and for identifying depositional systems, is a relatively new method, and thus can serve as a reference for other studies of similar facies assortment.

4

Trace fossils accompanying possible "Ediacaran organisms" in the Middle Cambrian sediments of the St. Petersburg Region, Russia

Natalin N., Mikulas R., Dronov A.

Acta Geologica Polonica

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2010

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Vol. 60, no. 1

71-76

EN

Shallow-marine Middle Cambrian sandy sediments of the St. Petersburg Region (i.e., sedimentary cover of the Baltic Shield) bear non-shelly, cup-like fossils, interpreted tentatively as descendants of Ediacaran organisms. The ichnoassemblage accompanying this occurrence consists of Skolithos, Diplocraterion and indeterminate biogenic sedimentary structures. The ichnofabric index is low (1-2). The probable body fossils are crosscut by the trace fossils. Though simple, the ichnoassemblage recorded here yields valuable information on the environment that could have hosted Ediacaran organisms during the earliest Phanerozoic.

5

Three-dimensionally integrated trace fossils from shallow-marine deposits in the Lower Cretaceous of the Neuquen Basin (Argentina) : Hillichnus agrioensis isp. nov.

Pazos P., Fernandez D.

Acta Geologica Polonica

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2010

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Vol. 60, no. 1

105-118

EN

A complex trace fossil that requires a three-dimensional (3D) reconstruction is described and interpreted. The specimens studied are assigned to a new ichnospecies (Hillichnus agrioensis) of Hillichnus Bromley et al., 2003. Most of them are uncollectable and a compound iconotype was designed to characterise the new ichnospecies. The three-dimensional trace fossil has been recorded in marginal-marine deposits close to the top of the Agrio Formation (Lower Cretaceous of Neuquen Basin, Argentina). The new ichnospecies shows a different pattern of feeding than H. lobosensis Bromley et al., 2003, and records defaecation downward in the deeper preservational level (level 4). Feather-like structures (level 2) that typify the ichnogenus also record the activity of an inhalant siphon and indicate a retractile movement. The vertical shafts (level 1) are scarcely recorded. Aligned double rings also document the infaunal habit of the tellinid bivalves that are considered the most likely producers of the trace. It is clear that when only level 2 is exposed, in some cases this form can be assigned to Jamesonichnites heinbergi Dam 1990a consequently, this ichnospecies is interconnected with more than one ichnogenus. Vertical projections recorded in branches differ from the type ichnospecies H. lobosensis Bromley et al., 2003. The occurrence in marginal-marine facies is congruent with the record of Jamesonichnites but not common in the type species and similar to those more frequent in deep-sea deposits (e.g. Polykampton alpinum Ooster, 1869).

6

Computation of flow around inland waterway vessel in shallow water

Tabaczek T.

Archives of Civil and Mechanical Engineering

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2008

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Vol. 8, no 1

99-107

EN

Flow around an inland waterway vessel in shallow water was computed in model scale using CFD software Fluent. Theoretical data were compared to the results of measurements in towing tank. The comparison comprises ship resistance, wave profile on hull surface, and distribution of velocity in tlow around bow and stern.

PL

Przy użyciu programu komputerowego Fluent obliczany był przepływ wokół kadłuba statku śródlądowego w skali modelu. Wyniki obliczeń zostały porównane z wynikami pomiarów w basenie holowniczym. Porównanie obejmuje opór kadłuba, profil fali na powierzchni kadłuba i rozkład prędkości przepływu w pobliżu dziobu i rufy.

7

Assessment of ship squat in shallow water using CFD

Jachowski J.

Archives of Civil and Mechanical Engineering

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2008

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Vol. 8, no 1

19-38

EN

In the recent years much research effort in ship hydromechanics is devoted to the practical navigation problems in getting larger ships safely into existing harbours or to the appropriate design of expansion of harbours for safe accommodation of larger ships. 80th these problems are directly related to the safety of navigation and therefore they receive high attention from ship designers. harbour designers. ship operators and maritime administration. The starting point of any navigational or design analysis lies in the accurate determination of the hydrodynamic forces generated on the ship hull moving in confined waters. The analysis of such ship motion should include the effects of shallow water, horizontal restrictions, asymmetric channels, muddy bottoms. ship squat. ship to ship interactions etc. It is natural to use advanced Computational Fluid Dynamics methods for this purpose. The paper includes a wide introduction into the problems of modelling of the restricted water effects on ship motion using CFD. This presentation is illustrated with the examples of calculations performed using the commercial system Fluent.

PL

W ostatnich latach przeprowadzone zostały liczne badania mające na celu identyfikacje sił hydrodynamicznych działających na manewrujący statek na akwenach portowych przystosowanych dla dużych statków. Problemy związane z bezpieczeństwem nawigacji na tych akwenach odgrywają ważną rolę w projektowaniu akwenów i są przedmiotem badań organizacji morskich. U podstaw jakiejkolwiek nawigacji i analizy projektów leży odpowiednie określenie sił hydrodynamicznych generowanych przez kadłub poruszający się na wodach ograniczonych. Analiza ta powinna zawierać przede wszystkim efekt osiadania, poziome ograniczenia kanałów, dna akwenów, oddziaływania kadłubów mijających się statków itp. Jest więc oczywiste, że do badań w tej dziedzinie stosuje się zaawansowane metody numerycznej mechaniki płynów. Artykuł zawiera wstęp do problemu modelowania efektów wody ograniczonej przy użyciu komercyjnego programu Fluent.