Search results for: UNDERWATER ACOUSTIC CHANNEL - Bridge of Knowledge

Search

Search results for: UNDERWATER ACOUSTIC CHANNEL

Search results for: UNDERWATER ACOUSTIC CHANNEL

  • A simplified channel estimation procedure for NB-IoT downlink

    Publication

    - Year 2024

    This paper presents a low-complexity channel estimation procedure which is suitable for use in energy-efficient NB-IoT user equipment devices. The procedure is based on the well-established least squares scheme, followed by linear interpolation in the time domain and averaging in the frequency domain. The quality of channel estimation vs. signal-to-noise ratio is evaluated for two channel models and compared with the performance...

    Full text available to download

  • Interaction between acoustic and non-acoustic mode in bubbly liquid

    Publication

    The nonlinear interaction of acoustic and entropy modes in a bubbly liquid is the subject of investigation. Thedynamic equation governing an excess density of the entropy mode is derived. Nonlinearity and dispersion are the reasons forexcitation of the entropy mode. The nonlinear interaction of modes as a reason for bubble to grow due to sound, is discovered.Some numerical examples of the modes interactions are made.

    Full text to download in external service

  • Smart acoustic band structures

    Publication

    Smart acoustic band structures exhibit very interesting and non-standard physical properties due to the periodic nature of their certain characteristic on different scale levels. They manifest mostly in their frequency spectra as socalled frequency band-gaps or stop-bands, what has a great impact on the behaviour of these structures in relation to the propagation of vibro-acoustic signals that can be transmitted through the structures...

    Full text to download in external service

  • A simple test for quantum channel capacity

    Publication

    Based on state and channel isomorphism we point out that semidefiniteprogramming can be used as a quick test for nonzero one-way quantum channelcapacity. This can be achieved by searching for symmetric extensions of statesisomorphic to a given quantum channel. With this method we provide examplesof quantum channels that can lead to high entanglement transmission but stillhave zero one-way capacity, in particular, regions of symmetric...

    Full text to download in external service

  • Interaction of Acoustic and Thermal Modes in the Vibrationally Relaxing Gases. Acoustic Cooling

    Publication

    The dynamic equation which governs an excess temperature associated with the thermal mode in vibrationally relaxing gas is derived. The nonlinear transfer of acoustic energy to the energy of the thermal mode in a relaxing gas causes slow variation of temperature with time. The nal dynamic equation is instantaneous. All types of sound, including aperiodic, may be considered as an acoustic source of corresponding heating or cooling....

    Full text available to download

  • A Simplistic Downlink Channel Estimation Method for NB-IoT

    Publication

    This paper presents a downlink channel estimation method intended for a Narrowband Internet of Things (NB-IoT) access link. Due to its low computational complexity, this method is well suited for energy-efficient IoT devices, still providing acceptable reception quality in terms of signal-to-noise (SNR) performance. This paper describes the physical layer of NB-IoT within the scope of channel estimation, and also reviews existing...

    Full text available to download

  • On the Characteristic Graph of a Discrete Symmetric Channel

    We present some characterizations of characteristic graphs of row and/or column symmetric channels. We also give a polynomial-time algorithm that decides whether there exists a discrete symmetric channel whose characteristic graph is equal to a given input graph. In addition, we show several applications of our results.

    Full text to download in external service

  • Integration of inertial sensors and GPS system data for underwater navigation

    The 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...

    Full text available to download

  • Small rov to detection and identification of dangerous underwater objects

    Publication

    - Year 2011

    A small unmanned underwater vehicle (UUV) to inspection of an undersea space is presented in the paper. Its behavior is controlled by a trained pilot. Correct detection and identification of targets depends on vehicle'sprecise displacement along a predefined route. Nowadays, the UUVs are equipped with an automatic control system to execute some basic maneuvers without constant human interventions. Hence, in the paper, an autopilot...

    Full text to download in external service

  • Interaction of Acoustic and Thermal Modes in the Gas with Nonequilibrium Chemical Reactions: Possibilities of Acoustic Cooling

    Nonlinear generation of thermal mode during propagation of dominative sound in a chemically reacting gas is considered. The dynamic equation of excess temperature associated with the thermal mode is derived. It is instantaneous and includes quadratic nonlinear acoustic source reflecting the nonlinear character of interaction between acoustic and non-acoustic types of gas motion. Both periodic and aperiodic sound may be considered...

    Full text to download in external service

  • Local buckling of composite channel columns

    The investigation concerns local buckling of compressed flanges of axially compressed composite channel columns. Cooperation of the member flange and web is taken into account here. The buckling mode of the member flange is defined by rotation angle a flange about the line of its connection with the web. The channel column under investigation is made of unidirectional fibre-reinforced laminate. Two approaches to member orthotropic...

    Full text available to download

  • Acoustic heating produced in the boundary layer

    : Instantaneous acoustic heating of a viscous fluid flow in a boundary layer is the subject of investigation. The governing equation of acoustic heating is derived by means of a special linear combination of conservation equations in the differential form, which reduces all acoustic terms in the linear part of the final equation but preserves terms belonging to the thermal mode. The procedure of decomposition is valid in a weakly...

    Full text available to download

  • Detection, classification and localization of acoustic events in the presence of background noise for acoustic surveillance of hazardous situations

    Evaluation of sound event detection, classification and localization of hazardous acoustic events in the presence of background noise of different types and changing intensities is presented. The methods for discerning between the events being in focus and the acoustic background are introduced. The classifier, based on a Support Vector Machine algorithm, is described. The set of features and samples used for the training of the...

    Full text available to download

  • Dissimilar underwater wet welding of HSLA steels

    The high-strength low-alloy S460ML and S460N steels were chosen for underwater wet welding of dissimilar T-joints using covered electrodes. For improving the quality of joints, the temper bead welding (TBW) method was used. The application of TBW in pad welding conditions has been investigated earlier but the possibility of usage of this technique in welded joints was not analyzed. The main aim of the study was to check the influence...

    Full text available to download

  • Detection and localization of selected acoustic events in acoustic field for smart surveillance applications

    A method for automatic determination of position of chosen sound events such as speech signals and impulse sounds in 3-dimensional space is presented. The evens are localized in the presence of sound reflections employing acoustic vector sensors. Human voice and impulsive sounds are detected using adaptive detectors based on modified peak-valley difference (PVD) parameter and sound pressure level. Localization based on signals...

    Full text available to download

  • CFD and FEM model of an underwater vehicle propeller

    During the project execution of design and optimization the Remotely Operated Vehicle (ROV) research on its propulsion has been carried out. The entire project was supported by CFD and FEM calculations, which taking into account the characteristics of underwater vehicle. One of the tasks was to optimize the semi-open duct for horizontal propellers, which provided propulsion and controllability in horizontal plane. In order to...

    Full text available to download

  • Efficiency of acoustic heating in the Maxwell fluid

    Publication

    The nonlinear effects of sound in a fluid describing by the Maxwell model of the viscous stress tensor is the subject of investigation. Among other, viscoelastic biological media belong to this non-newtonian type of fluids. Generation of heating of the medium caused by nonlinear transfer of acoustic energy, is discussed in details. The governing equation of acoustic heating is derived by means of the special linear combination...

    Full text available to download

  • Efficiency of acoustic heating in the Maxwell fluid

    Publication

    The nonlinear effects of sound in a fluid describing by the Maxwell model of the viscous stress tensor is the subject of investigation. Among other, viscoelastic biological media belong to this non-newtonian type of fluids. Generation of heating of the medium caused by nonlinear transfer of acoustic energy, is discussed in details. The governing equation of acoustic heating is derived by means of the special linear combination...

    Full text available to download

  • Propagation of Acoustic Disturbances in Shallow Sea

    Publication

    - Year 2013

    Propagation of acoustic waves in shallow sea differs fundamentally from the same phenomenon occurring in deep sea in view of non-negligible distance from the sea bottom in the first case, where presence of two regions limiting the water layer results in the acoustic pressure distribution induced by a harmonic source has an interferential nature as a result of multi-path propagation of the acoustic signal. These interferential properties...

  • Detection and localization of selected acoustic events in 3D acoustic field for smart surveillance applications

    A method for automatic determination of position of chosen sound events such as speech signals and impulse sounds in 3-dimensional space is presented. The events are localized in the presence of sound reflections employing acoustic vector sensors. Human voice and impulsive sounds are detected using adaptive detectors based on modified peak-valley difference (PVD) parameter and sound pressure level. Localization based on signals...

    Full text to download in external service

  • Characteristics of the polarised off-body channel in indoor environments

    Publication

    This paper addresses the depolarisation effect in off-body body area networks channels, based on measurements performed at 2.45 GHz in an indoor environment. Seven different scenarios, involving both static and dynamic users, were considered, taking a statistical perspective. The analysis of the cross-polarisation discrimination is performed, as well as the analysis of path loss in co- and cross-polarised channels. Results show...

    Full text available to download

  • Bead-on-Plate Underwater Wet Welding on S700MC Steel

    The participation of high strength steels in marine and offshore structures is increasing, which makes it necessary to develop recommendations for underwater repair welding works. The article presents the results of bead-on-plate welded specimens made of S700MC high strength steel in underwater wet welding conditions by covered elec- trodes. Three specimens with heat input values in the range 0.91-1.05 kJ/mm were made. The specimens...

    Full text available to download

  • Wideband Off-Body Channel Characteristics with Dynamic User

    Publication

    - Year 2019

    This paper presents the preliminary results of a dynamic off-body channel characterisation study, based on wideband measurements at 5.8 GHz in an indoor environment. The Channel Impulse Response (CIR) was measured for a scenario with the user approaching and departing from the off-body antenna. A CIR deconvolution procedure was performed jointly in two polarisations, and the received signal power, Cross-Polarisation Discrimination...

  • Long-term comparative evaluation of an acoustic climate in selected schools before and after the acoustic treatment

    The results of long-term continuous noise measurements in two selected schools are presented in the paper. Noise characteristics were measured continuously there for approximately 16 months. Measurements started eight months prior to the acoustic treatment of the school corridors of both schools. An evaluation of the acoustic climates in both schools, before and after the acoustic treatment, was performed based on comparison of...

    Full text available to download

  • Steady magnetohydrodynamic flow in a diverging channel with suction or blowing

    Publication

    - ZEITSCHRIFT FUR ANGEWANDTE MATHEMATIK UND PHYSIK - Year 2013

    An analysis is made of steady two-dimensional divergent flow of an electrically conducting incompressible viscous fluid in a channel formed by two non-parallel walls, the flow being caused by a source of fluid volume at the intersection of the walls. The fluid is permeated by a magnetic field produced by an electric current along the line of intersection of the channel walls. The walls are porous and subjected to either suction...

    Full text to download in external service

  • Role of bead sequence in underwater welding

    Publication

    This paper presents examinations of the role of the bead sequence in underwater welding. Two specimens of wet welded layers made by covered electrodes with the use of normalized S355G10+N steel were welded by a reasonable bead sequence. For each specimen, metallographic macro- and micro-scopic tests were done. Then, Vickers HV10 hardness measurements were conducted for each pad weld in the welded layer. The results show that welding...

    Full text available to download

  • Sławomir Jerzy Ambroziak dr hab. inż.

    Sławomir J. Ambroziak was born in Poland, in 1982. He received the M.Sc., Ph.D. and D.Sc. degrees in radio communication from Gdańsk University of Technology (Gdańsk Tech), Poland, in 2008, 2013, and 2020 respectively. Since 2008 he is with the Department of Radiocommunication Systems and Networks of the Gdańsk Tech: 2008-2013 as Research Assistant, 2013-2020 as Assistant Professor, and since 2020 as Associate Professor. He is...

  • THE EFFECT OF WET UNDERWATER WELDING ON COLD CRACKING SUSCEPTIBILITY OF DUPLEX STAINLESS STEEL

    ABSTRACT The present work was conducted to assess the weldability of duplex stainless steel in underwater conditions. Metal manual arc welding (MMA) with the use of coated electrodes was used in the investigations. Tekken weldability tests were performed underwater at 0.5 m depth and in the air. Nondestructive tests, metallographic examinations of welds, ferrite content assessment in microstructure and hardness test were performed....

    Full text available to download

  • Detection of the acoustic interferences during AFM operation

    Open Research Data

    Atomic force microscopy is a particularly complicated surface imaging technique due to the large number of factors that affect the quality of the resulting images. They are obviously difficult and sometimes even impossible to control at the same time. One of such factors may even be the seismological location of the building or the influence of mechanical...

  • A New Fuzzy Sliding Mode Controller with PID Sliding Surface for Underwater Manipulators

    Publication

    Design 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...

  • Assessment of the Accuracy of a Virtual Multi-Channel Temperature Measuring Instrument

    Publication

    The multi-channel temperature measurement system developed works with NTC thermistors. The article presents the results of theoretical and empirical evaluation of accuracy obtained in measurement channels. The basis for the theoretical assessment is the mathematical model for each of the measurement channels and the characteristics of the system elements included in the circuits of the measurement channel. Two different methods were...

    Full text available to download

  • Influence of selected additives and admixtures on underwater concrete and the environment

    Publication

    - MATEC Web of Conferences - Year 2018

    The intensive civilization development has an influence on searching for new possibilities connected with extension of city agglomerations, both the areas of flat building and the industrial areas. One of the most interesting solution is to use water reservoirs, rivers and sea areas. The extension of buildings has an influence on building materials, especially hydrotechnical, which means development of production of hydrotechnical...

    Full text available to download

  • 3D Imaging Of Underwater Objects Using Multi-Beam Data

    Publication

    One 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)...

    Full text available to download

  • Underwater Local Cavity Welding of S460N Steel

    In this paper, a comparison of the mechanical properties of high-strength low-alloy S460Nsteel welded joints is presented. The welded joints were made by the gas metal arc welding (GMAW)process in the air environment and water, by the local cavity welding method. Welded joints were testedfollowing the EN ISO 15614-1:2017 standard. After welding, the non-destructive—visual, penetrant,radiographic, and ultrasonic (phased array) tests...

    Full text available to download

  • Triangular 3D Laser Scanning in Underwater Photogrammetry

    The use of triangular 3D laser scanning may significantly enhance the visual inspection of underwater objects. In these days of high demand for accurate information, exclusively photographic documentation is not enough, as it is geometrically flawed. The authors of this article are trying to present the rudiments of laser scanning, a modern means of measuring, which is reliable, relatively easy to use and works in accordance with...

    Full text available to download

  • Acoustic journal bearing - A search for adequate configuration

    Classical non-contact bearings are already used in a number of specialist applications but there are somespecialist areas where they cannot be used for variety of reasons and acoustic sliding bearings could be an alternative. The paper presents the quest for a configuration of an acoustic journal bearing and shows that the overall shape of the bearing and its geometry are of a vital importance for the load capacity oft he bearing....

    Full text to download in external service

  • Underwater Wet Repair Welding of API 5L X65M Pipeline Steel

    This 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...

    Full text available to download

  • Characteristics of the Polarised Off-Body Channel in Indoor Environments

    Publication

    - Year 2016

    This paper addresses the depolarisation effect in off-body Body Area Networks channels, based on measurements performed at 2.45 GHz in an indoor environment. Seven different scenarios, involving both static and dynamic users, were considered, taking a statistical perspective. The analysis of the cross-polarisation discrimination is performed, as well as the analysis of path loss in co- and cross-polarised channels. Results show...

  • Piotr Szczuko dr hab. inż.

    Piotr Szczuko received his M.Sc. degree in 2002. His thesis was dedicated to examination of correlation phenomena between perception of sound and vision for surround sound and digital image. He finished Ph.D. studies in 2007 and one year later completed a dissertation "Application of Fuzzy Rules in Computer Character Animation" that received award of Prime Minister of Poland. His interests include: processing of audio and video, computer...

  • Autonomous Control of the Underwater Remotely Operated Vehicle in Collision Situation with Stationary Obstacle

    Publication

    - Polish Maritime Research - Year 2022

    The article considers the problem of autonomous control of the underwater remotely operated vehicle mini Remotely Operated Vehicle (ROV) in a collision situation with a stationary obstacle. The control of the collision avoidance process is presented as a synthesis of fuzzy proportional-differential controllers for the control of distance and orientation concerning the detected stationary obstacle. The control of the submergence...

    Full text available to download

  • Multi-Channel Virtual Instrument for Measuring Temperature—A Case Study

    Publication

    - Electronics - Year 2023

    The article presents the hardware and software configuration of the developed multi-channel temperature measurement system as well as calibration procedures and measurement results verifying the properties of measurement channels. The system has been developed and dedicated primarily for measuring the temperature distribution in a laboratory model simulating underground power lines. With the adopted configuration of the analog...

    Full text available to download

  • Acoustic heating produced in resonators filled by a newtonian fluid

    Publication

    Acoustic heating in resonators is studied. The governing equation of acoustic heating is derived by means of the special linear combination of conservation equations in differential form, allowing the reduction of all acoustic terms in the linear part of the final equation, but preserving terms belonging to the thermal mode responsible for heating. This equation is instantaneous and includes nonlinear acoustic terms that form a...

    Full text available to download

  • The Examination of the Upper Layers of the Seabed by the Means of the Acoustic Methods

    Publication

    Propagation of acoustic waves in the sea, in particular in shallow sea, depends on several factors. The basic of them are source power and frequency of acoustic waves, spatial distribution inhomogeneous medium in which acoustic wave propagates, and distributions of speed of sound and density of seawater. The coastal conditions, which limit water medium from above (free surface of the sea) and from bottom (the seabed), are no less...

    Full text available to download

  • Underwater wet welding of S1300 ultra-high strength steel

    Marine 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...

    Full text available to download

  • Modelling of acoustic backscattering by southern Baltic herring

    Publication

    - HYDROACOUSTICS - Year 2016

    Assessment of Baltic herring abundance can be carried out using acoustic techniques. Analysis of the relationship between the Baltic herring individual target strength, TS, and the total fish length, L, important for the acoustic assessment, showed the relationship to be dependent on the location of the study area. This finding motivated a detailed analysis of the relationship for the herring occurring in the southern Baltic...

    Full text to download in external service

  • Reconstruction Methods for 3D Underwater Objects Using Point Cloud Data

    Publication

    Existing 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....

    Full text available to download

  • Acoustic heating produced in the thermoviscous flow of a bingham plastic

    This study is devoted to the instantaneous acoustic heating of a Bingham plastic. The model of the Bingham plastic's viscous stress tensor includes the yield stress along with the shear viscosity, which differentiates a Bingham plastic from a viscous Newtonian fluid. A special linear combination of the conservation equations in differential form makes it possible to reduce all acoustic terms in the linear part of of the final equation...

    Full text available to download

  • Acoustic heating produced in the thermoviscous flow of a Bingham plastic

    This study is devoted to the instantaneous acoustic heating of a Bingham plastic. The model of the Bingham plastic's viscous stress tensor includes the yield stress along with the shear viscosity, which differentiates a Bingham plastic from a viscous Newtonian fluid. A special linear combination of the conservation equations in differential form makes it possible to reduce all acoustic terms in the linear part of of the final equation...

    Full text available to download

  • Wideband Channel Measurements for Polarised Indoor Off-Body Communications

    Publication

    - Year 2018

    This paper presents the initial results of wideband channel measurements for polarised off-body communication at 5.8 GHz, in an indoor environment. Channel Impulse Response measurements were performed simultaneously for two orthogonal polarisations of the wearable antenna, and repeated for vertical and horizontal orientations of the off-body one. Four types of measurement scenarios were considered in order to investigate the influence...

  • SLIDING MODE-PID FUZZY CONTROLLER WITH A NEW REACHING MODE FOR UNDERWATER ROBOTIC MANIPULATORS

    Design of an accurate and robust controller is a challenging topic in an 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...