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wszystkich: 931
Wyniki wyszukiwania dla: UNDERWATER CONCRETE
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Reliable underwater communication system for shallow coastal waters
PublikacjaThis paper presents a reliable and robust low data rate spread spectrum approach which is implemented in the acoustic underwater communication system for shallow coastal waters. It shows operation assumptions of spread spectrum techniques based on the wellknown Shannon equation. It describes two methods of spread spectrum: frequency hopping spread spectrum and direct sequence spread spectrum; their block diagram and their characteristics...
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Adaptation of telecommunication modem techniques for underwater communication systems.
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Estimation of Coherence Bandwidth for Underwater Acoustic Communication Channel
PublikacjaA shallow underwater acoustic communication channel is characterized by strong multipath propagation. The signal reaching the receiver consists of a direct waveform and a number of its delayed and suppressed replica. A significant time dispersion of the transmitted signal and selective fading of its spectrum are observed. Coherence bandwidth defines maximal bandwidth, wherein the channel amplitude characteristic remains constant...
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Archaeologia Maritima Mediterranea. An International Journal on Underwater Archaeology
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New Contree
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Underwater acoustic communications system with error correction and synchronization coding
PublikacjaNiezawodna transmisja danych w wielodrogowym i niestacjonarnym płytkim kanale podwodnym wymaga zastosowania efektywnej techniki modulacji oraz equalizacji adaptacyjnej. W zaproponowanym artykule w systemie transmisji danych zastosowano modulację OFDM oraz equalizację adaptacyjną opartą o filtrację Kalmana. Ponadto zaimplementowano dwie techniki kodowania: FEC w celu eliminacji błędów transmisji oraz kodowanie pseudoszumowe, którego...
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Digital Signal Processing for Hydroacoustic System in Biomimetic Underwater Vehicle
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Underwater wet welding of S1300 ultra-high strength steel
PublikacjaMarine Structures Volume 81, January 2022, 103120 Underwater wet welding of S1300 ultra-high strength steel Author links open overlay panelJacekTomkówGrzegorzRogalski https://doi.org/10.1016/j.marstruc.2021.103120 Get rights and content Under a Creative Commons licenseopen access Highlights • Technological method of S1300 steel underwater weldability improving was proposed. • Number of cracks and hardness of welded joints was...
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3D Imaging Of Underwater Objects Using Multi-Beam Data
PublikacjaOne of the main applications of multibeam sonars is high resolution bathymetry measurement, as well as detecting and imaging of underwater objects like shipwrecks. In order to obtain the visualisation quality good enough to allow the researcher to investigate an object in more detail, the approach relying on construction of three-dimensional model of an imaged object, e.g. consisting of nodes, edges and plane elements (facets)...
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Integration of inertial sensors and GPS system data for underwater navigation
PublikacjaThe Inertial Navigation System (INS) is usually employed to determine the position of an underwater vehicles, like Remotely Operated Vehicles (ROV) and, more recently, Autonomous Underwater Vehicle (AUV). The accuracy of the position provided by the INS, which uses accelerometers and gyroscopes, deteriorates with time. An external aiding sources such as the Global Positioning System (GPS) can be employed to reduce the error growth...
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Modeling of active fiber Bragg grating underwater acoustic sensor.
PublikacjaW pracy przedstawiono wyniki modelowania nowego typu przetwornika hydroakustycznego wykorzystującego światłowodową siatkę Bragga. Siatka ta, domieszkowana jonami pierwiastków ziem rzadkich, pracuje jako laser z rozłożonym sprzężeniem zwrotnym, co pozwala na znaczne zwiększenie czułości tego prztwornika w porównaniu z rozwiązaniami wykorzystującymi siatki pasywne. W celu uzyskania równomiernego rozkładu naprężeń siatki zastosowano...
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Underwater Navigation System Based on Doppler Shifts of a Continuous Wave
PublikacjaThe paper describes a concept of an underwater navigation system designed to determine the location and speed of its ROVs or divers. Conducted by the Department of Marine Electronic Systems at the Gdansk University of Technology for several years, research has focused on navigation systems which determine positions on the basis of Doppler shifts of echo signals reflected from a moving object. This article presents a different version...
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Synchronization system for underwater acoustic communications using in shallow waters
PublikacjaA 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....
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Investigation of the underwater noise produced by ships by means of intensity method
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Limitations of WSSUS modeling of stationary underwater acoustic communication channel
PublikacjaPerformances of underwater acoustic communication (UAC) systems are strongly related to specific propagation conditions of the underwater channel. Due to their large variability, there is a need for adaptive matching of the UAC systems signaling to the transmission properties of the channel. This requires a knowledge of instantaneous channel characteristics, in terms of the specific parameters of stochastic models. The wide-sense...
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Comparison between measured and calculated underwater pressure of merchant ship
PublikacjaFrom 2012 The Polish Naval Academy take part in an international research project SIRAMIS, carried out in the framework of the European Defence Agency. The objective of this project is to improve the understanding of ship signature interaction with multi influence sensors in relevant and realistic scenario's. This paper describes selected results of the comparison results of sea trials and model calculations of the hydrodynamic...
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CEMENT AND CONCRETE RESEARCH
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Acoustic emission signals in concrete beams under 3-point bending (plain concrete, steel fibre reinforced concrete, steel bar reinforced concrete)
Dane BadawczeThe DataSet contains the results of the mechanical behaviour of concrete beams with dimensions 40 x 40 x 160 cm3under the 3-point bending. Two concrete mixes, both based on the same design, were produced in the test programme. Mixture #1 was the plain concrete (PC), consisting of cement CEM I 42.5R (380 kg/m3), water (165 kg/m3), aggregate 0/2 mm (648...
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Fresh properties of concrete mixes M0-M100 concrete mixes
Dane BadawczeDataset of fresh properties of concretes containing different amount of magnetite aggregate (M0-M100) mixes.*. ODS - open-source spreadsheet file file consists results of:
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Mechanical properties of concrete mixes M0-M100 concrete mixes
Dane BadawczeDataset of hardneded properties of concretes containing different amount of magnetite aggregate (M0-M100) mixes.Excel file consists results of:
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Evaluation of Mechanical Properties of Two-Stage Concrete and Conventional Concrete Using Nondestructive Tests
PublikacjaDifferent types of concrete mixtures are used as building materials. The manufacturing process of two-stage concrete (TSC) differs from that of conventional concrete. This study investigated conventional mechanical properties derive empirical relations for estimation of the mechanical parameters of TSC and conventional concrete mixtures. TSC was used to prepare 216 specimens and conventional concrete was used to prepare 108 specimens...
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Effect of welding conditions on susceptibility to cold cracking of underwater welded joints
PublikacjaPrzedstawiono wybrane aspekty spawalności stali przy spawaniu pod wodą metodą lokalnej komory suchej. Zwrócono szczególną uwagę na skłonność do tworzenia peknięć zimnych w SWC. Przy pomocy planowania doświadczeń określono ilościowy wpływ parametrów spawania na naprężenia krytyczne z próby implant.
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Influence of Fin’s Material Capabilities on the Propulsion System of Biomimetic Underwater Vehicle
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Underwater Wet Repair Welding of API 5L X65M Pipeline Steel
PublikacjaThis paper presents results of the research of effect of polymer insulation of pipeline made of API 5L X65M steel as well as underwater wet welding parameters on properties of joints made by covered electrodes. Effect of heat input on structure and hardness of joints during repair of underwater pipeline was analyzed. Welding defects like microcracks, micro-lacks of fusion, slag inclusions, as well as HAZ hardness increase over...
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Reconstruction Methods for 3D Underwater Objects Using Point Cloud Data
PublikacjaExisting methods for visualizing underwater objects in three dimensions are usually based on displaying the imaged objects either as unorganised point sets or in the form of edges connecting the points in a trivial way. To allow the researcher to recognise more details and characteristic features of an investigated object, the visualization quality may be improved by transforming the unordered point clouds into higher order structures....
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Effect of electrode waterproof coating on quality of underwater wet welded joints
PublikacjaIn this paper, the effects of different hydrophobic coatings on the surface of covered electrodes on the quality of wet welded carbon steel joints were discussed. Commonly available hydrophobic substances used in industrial applications were selected for the research. The aim of using waterproof coatings was to check the possibility to decreasing the susceptibility of highstrength low-alloy S460N steel to cold cracking. During...
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Underwater Navigation Ssystem Based on Doppler Shift – Measurements and Error Estimations
PublikacjaA new acoustic navigation system was developed to determine the position and speed of moving underwater objects such as divers and underwater vehicles. The path of an object and its speed were determined by the Doppler shifts of acoustic signals emitted by a transmitter placed on the object and received by four hydrophones installed at the periphery of the monitored body of water. The position and speed measurements were affected...
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Performance of Coherent Modulation Scheme Used in Acoustic Underwater Communication System
PublikacjaThe development of an acoustic underwater communication system for shallow waters is still a big scientificand construction challenge. Currently, non-coherent modulations in combination with strong channel coding are used to achieve reliable communication with low rate in such a channel. To obtain transmission with a higher transmission rate, it is required to use coherent modulation. This paper presents the assumptions of such...
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Tracking of the broadband source of the underwater noise in the very shallow water conditions
PublikacjaThe paper contains the result s, both theoretical and experimental , connected with the tracking of the underwater noise source as small ships, pontoon , diver and so on. The pro blem of security in the shallow water area is the challenge for underwater acousticians. In this paper there is take n into account the detection of the sources that move on the surface of the sea or underwater in shallow...
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Weldability of S460ML High Strength Low Alloy Steel in Underwater Conditions
PublikacjaThe paper presents experimental evaluation of susceptibility of the high strength S460ML steel to cold cracking in the conditions of wet welding with the use of covered electrodes. From the results of Tekken tests it was found out that the investigated steel was characterised, in the conditions of the carried out experiments (underwater wet welding and air welding with rutile electrodes), of high susceptibility to cold cracking....
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Artificial neural network controller for underwater ship hull operation robot.
PublikacjaZaproponowano model matematyczny pojazdu podwodnego, który w uproszczonej wersji spełnia warunki dynamiki odpowiadające głowicy roboczej podwodnego robota. Uwzględniono niektóre czynniki oddziałujące na ruch podwodnej głowicy roboczej, jak np. gęstość wody oraz siły odśrodkowe i wypornościowe. Przedstawiono układ sterowania, w którym zastosowano regulator oparty na bazie sieci neuronowych, za pomocą którego można sterować...
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Underwater communication system for shallow water using modified MFSK modulation
PublikacjaOpisano budowę i zasadę działania systemu komunikacji podwodnej z modulacją MMFSK. System służy do przekazywania danych i komend ze statku do obiektów podwodnych w płytkich wodach przybrzeżnych i jeziorach. Priorytetowe wymagania postawione systemowi to bardzo małe zużycie energii w części podwodnej i bardzo mała liczba błędów transmisji. Szczególną uwagę zwrócono na nietypowe źródło błędów, jakim są zniekształcenia nieliniowe...
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The kinematic model of the novel autonomous underwater robot for ship hull cleaning
PublikacjaOmówiono zagadnienia związane ze sterowaniem autonomicznego robota podwodnego przeznaczonego do oczyszczania kadłuba statku z bioporostów. Dokonano przeglądu wybranych prac na temat systemów lokalizacji i algorytmów sterowania robotów podwodnych oraz przedstawiono projekt własny, w którym zawarto opis obiektu podwodnego przemieszczającego się po ustalonym torze. Dla określonych warunków roboczych zaproponowano koncepcję metody...
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Probe signal processing for channel estimation in underwater acoustic communication system
PublikacjaUnderwater acoustic communication channels are characterized by a large variety of propagation conditions. Designing a reliable communication system requires knowledge of the transmission parameters of the channel, namely multipath delay spread, Doppler spread, coherence time, and coherence bandwidth. However, the possibilities of its estimation in a realtime underwater communication system are limited, mainly due to the computational...
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Testing the Wide-Sense Stationarity of Bandpass Signals for Underwater Acoustic Communications
PublikacjaThe Underwater Acoustic Communication (UAC) systems work in communication channels characterized by a large variety of multipath propagation conditions that can additionally change over time. Designing a reliable communication system requires knowledge of the transmission parameters of the channel. There is a need for the development of adaptive signaling schemes that would dynamically optimize the signal parameters of the physical...
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Multiple-Input Multiple-Output Technique for Underwater Acoustic Communication System
PublikacjaThe performance of an underwater acoustic communication (UAC) system is limited due to tough propagation conditions in the UAC channel. Multiple-Input Multiple-Output (MIMO) technique can improve the reliability of the data transmission system, increase its speed, increase its range, and reduce the energy consumption. The paper presents an implementation method of MIMO technique in the form of coding the Space-Time Block Code and...
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Wake-Up Receiver for Underwater Acoustic Communication Using in Shallow Water
PublikacjaA data frame transmitted over the underwater acoustic channel usually begins with a preamble. Therefore, underwater communication systems have a dedicated receiver that constantly listens to the preamble signals. A receiver that is to work effectively in shallow waters must have solutions that effectively reduce the impact of the permanently occurring multipath propagation. The article presents a solution based on complementary...
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Simple empirical formula to estimate the main geomechanical parameters of preplaced aggregate concrete and conventional concrete
PublikacjaPreplaced aggregate concrete (PAC) or two-stage concrete is a specific type of concrete successfully employed in many projects including underwater concrete structures, massive concrete structures, structures made of reinforced concrete, and improvement of concrete structures. PAC is significantly different than the conventional concrete. In this type of concrete, aggregates are initially poured into the mold, the voids between...
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Underwater noise recorded in Hornsund Fjord, Spitsbergen, at the front of the Hans Glacier
Dane BadawczeThe data includes underwater noise recorded in Hornsund Fjord, Spitsbergen at the front of the Hans Glacier between 05/09/2013 and 30/09/2013. A description of the data is in the article
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Standard and modified falling mass impact tests on preplaced aggregatefibrous concrete and slurry infiltrated fibrous concrete
PublikacjaAlthough several studies have been conducted to evaluate the impact response of concrete using theAmerican Concrete Institute (ACI) 544-2R falling mass impact test, the variations in test results are themain drawback of this testing method. This study aims to reduce the variations in experimental impacttest results by introducing two simple test setup modifications; (1) using coarse or fine aggregate bed-ding as an alternative...
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Evaluation of the resistance of steel–concrete adhesive connection in reinforced concrete beams using guided wave propagation
PublikacjaThe development of the nondestructive diagnostic methods is of significant importance in the last decades. A special attention is paid to diagnostics of reinforced concrete structures, which are very popular in the civil engineering field. A possible use of the guided waves in the estimation of the resistance of steel–concrete adhesive connection is studied in the following paper. The relationships relating adhesive connection...
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Innovative Energy-Saving Propulsion System for Low-Speed Biomimetic Underwater Vehicles
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Comparison of Different Course Controllers of Biomimetic Underwater Vehicle with Two Tail Fins
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Innovative Energy-Saving Propulsion System for Low-Speed Biomimetic Underwater Vehicles
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A New Fuzzy Sliding Mode Controller with PID Sliding Surface for Underwater Manipulators
PublikacjaDesign of an accurate and robust controller is challenging topic in underwater manipulator control. This is due to hydrodynamic disturbances in underwater environment. In this paper a sliding mode control (SMC) included a PID sliding surface and fuzzy tunable gain is designed. In this proposed controller robustness property of SMC and fast response of PID are incorporated with fuzzy rules to reduce error tracking. In the control...
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3D Form analysis of rope deformation with long towed underwater hydroacoustic antenna
PublikacjaArtykuł opisuje rozwiązanie zagadnienia brzegowego dla zestawu długiej liny holującej i podwodnej anteny hydroakustycznej o gęstości, tej ostatniej, nieznacznie większej od gęstości wody i małej sztywności. Znane jest tylko położenie punktu zamocowania liny do okrętu (p-kt początkowy holowanego zestawu) oraz głębokość, na której znajduje się koniec anteny. Przedstawiono analizę sił działających na holowany zestaw, ich równania...
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Cold Cracking Of Underwater Wet Welded S355G10+N High Strength Steel
PublikacjaWater as the welding environment determines some essential problems influencing steel weldability. Underwater welding of high strength steel joints causes increase susceptibility to cold cracking, which is an effect of much faster heat transfer from the weld area and presence of diffusible hydrogen causing increased metal fragility. The paper evaluates the susceptibility to cold cracking of the high strength S355G10+N steel used,...
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Thermo-Mechanical Simulation of Underwater Friction Stir Welding of Low Carbon Steel
PublikacjaThis article investigates the flow of materials and weld formation during underwater friction stir welding (UFSW) of low carbon steel. A thermo-mechanical model is used to understand the relation between frictional heat phenomena during the welding and weld properties. To better understand the effects of the water environment, the simulation and experimental results were compared with the sample prepared by the traditional friction...
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Underwater acoustic communication system using broadband signal with hyperbolically modulated frequency
PublikacjaThe 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...
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A Method for Underwater Wireless Data Transmission in a Hydroacoustic Channel under NLOS Conditions
PublikacjaWireless data transmission in the hydroacoustic channel under non-line-of-sight (NLOS) propagation conditions, for example, during a wreck penetration, is difficult to implement reliably. This is mostly due to the multipath propagation, which causes a reduction in the quality of data reception. Therefore, in this work an attempt has been made to develop a reliable method of wireless underwater communication test it under the NLOS...