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wszystkich: 789
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Wyniki wyszukiwania dla: ACOUSTIC HYSTERESIS
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Acoustics - new services for urban planning, research and education
PublikacjaThe main purpose of the presented design is twofold, namely: providing detailed information about the noise threats that occur every day in city areas and preventing the noise induced hearing loss especially among young people. An experimental system designed for the continuous monitoring of the acoustic climate of urban areas was developed and implemented within the PLGrid Plus project. The assessment of environmental threats...
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Acoustical images of the Gulf of Gdansk
PublikacjaAcoustic images of seabed are of interest to specialists in the field of marine engineering, marine navigation, marine archeology, hydrogeology, etc. New technolo gies based on use of elastic waves, predominantly acoustic waves that allow detecting complexity of geometric forms of seabed, ensure progress in studying the bathymetric structure of seafloor. Use of parametric sources of waves generated...
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Computational investigations of acoustic radiation from end shields of small-power electric motor
PublikacjaW artykule omówiono rozwój metod modelowania własności akustycznych maszyn elektrycznych. Wskazano na pomijalny dotąd, znaczący udział drgań tarcz łożyskowych w emitowaniu hałasu przez silniki małej mocy. Na podstawie równania falowego potencjału prędkości wyprowadzono analityczne formuły do obliczeń akustycznych w polu bliskim tarczy łożyskowej. Zamieszczono uzyskane z serii obliczeń dla pracującego silnika, rozkłady ciśnienia...
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Time-Domain Description of Point-Source Acoustic Wavefields as a Useful Approach in Ultrasonic Techniques
PublikacjaIn traditional acoustics, field problems are usually treated in the frequency domain, broadband fields being reduced to superposition of harmonic spectrum components. However, this approach is inherently acausal and it is known that in case of arbitrary signals, the distribution-based, time-domain description can be more effective. The present paper is an attempt to expand the time-domain linear systems formalism onto space problems...
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Standing Acoustic Waves and Relative Nonlinear Phenomena in a Vibrationally Relaxing Gas-Filled Resonator
PublikacjaStanding acoustic waves in one-dimensional resonator filled with vibrationally relaxing gas, are studied. Two regimes of excitation of molecular vibrational degrees of freedom are considered, equilibrium and nonequilibrium. The acoustic energy enlarges with time in the non-equilibrium regime and decreases otherwise before formation of discontinuity. After that, it decreases due to nonlinear absorption and tends to zero in equilibrium...
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Improvement of glass break acoustic signal detection via application of wavelet packet decomposition
PublikacjaThe main subject of the authors' research are non-contact methods of glass break detection based on analysis of the acoustic signal generated during the event. This problem has essential meaning for modern cost- effective alarm systems, particularly those installed into big buildings. The main difficulties of the matter are: transient character of the signal, great number of similar sounds (false signals, mainly accidental glass...
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Geographic information system for remote integration of diverse under-water acoustic sensor data
PublikacjaMaritime and port areas throughout the world are exposed to many different hazards, like pollution, terrorism and natural disasters. Early detection, identification and preparation of appropriateesponse strategies is especially important in the case of semi-enclosed basins like the Baltic Sea, mainly due to the marine ecosystems' continuous absorption of pollutants including oil, heavy metals and chemicals. Many of those agents...
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Thermal Self-Action Effects of Acoustic Beam in a Gas with Reversible or Irreversible Chemical Reaction
PublikacjaThermal self-action of acoustic beam in a gas where an exothermic chemical reaction takes place, is studied. This kind of thermal self-action differs from that in a newtonian fluid. In dependence on the type of a chemical reaction, reversible or not, heating or cooling of a medium occurs. A beam in the case of the irreversible reaction may be unusually self-focusing. The self-action effects relating to wave beams containing shock...
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Time-domain description of point-source acoustic wavefields as a useful approach in ultrasonic techniques
PublikacjaIn traditional acoustics, field problems are usually treated in the frequency domain, broadband fields being reduced to superposition of harmonic spectrum components. However, this approach is inherently acausal and it is known that in case of arbitrary signals, the distribution-based, time-domain description can be more effective. The present paper is an attempt to expand the time-domain linear systems formalism onto space problems...
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Acoustic field and the entropy mode induced by it in a waveguide filled with some non-equilibrium gases
PublikacjaThe non-linear propagation of an acoustic beam in a rectangular waveguide is considered. The medium of sound propagation, is a gas where thermodynamically non-equilibrium processes take place: such as exothermic chemical reactions or excitation of vibrational degrees of a molecule’s freedom. The incident and reflected compounds of the acoustic field do not interact in the leading order in the case of periodic weakly nonlinear sound...
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Nonlinear generation of non-acoustic modes by low-frequency sound in a vibrationally relaxing gas
PublikacjaTwo dynamic equations referring to a weakly nonlinear and weakly dispersive flow of a gas in which molecular vibrational relaxation takes place. are derived. The first one governs an excess temperature associated with the thermal mode, and the second one describes variations in vibrational energy. Both quantities refer to non-wave types of gas motion. These variations are caused by the nonlinear transfer of acoustic energy into...
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Air journal bearing utilizing near-field acoustic levitation: stationary shaft case
PublikacjaResults of a study to examine a unique idea of self-levitating journal bearing are presented in this paper. the idea represents a radical departure from the current bearing technology. it utilisesacoustic levitation, which relies on the sound energy radiated by an object supporting a load. acoustic levitation has been demonstrated to support loads of up to 10 kg. in order to support a load theacoustic wave emitted by the radiating...
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Problem of proper decomposition and initialization of acoustic and entropy modes in a gas affected by the mass force
PublikacjaThe relations connecting perturbations specific for acoustic and entropy modes in an accelerated fluid or in a fluid affected by constant mass force, are derived. They allow to decompose the total vector of perturbations and the overall energy into acoustic and non-acoustic parts uniquely at any instant. In order to do this, three quantities are required, for example total perturbations in entropy, pressure and velocity. The evaluations...
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Automatic localization and continous tracking of mobile sound source using passive acoustic radar
PublikacjaA concept, practical realization and applications of the passive acoustic radar for localization and continuous tracking of fixed and mobile sound sources such as: cars, trucks, aircrafts and sources of shooting, explosions were presented in the paper. The device consists of the new kind of multi-channel miniature three dimensional sound intensity sensors invented by the Microflown company and a group of digital signal processing...
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Identification of acoustic event of selected noise sources in a long-term environmental monitoring systems
PublikacjaABSTRACT Undertaking long-term acoustic measurements on sites located near an airport is related to a problem of large quantities of recorded data, which very often represents information not related to flight operations. In such areas, usually defined as zone of limited use, often other sources of noise exist, such as roads or railway lines treated is such context as acoustic background. Manual verification of such recorded data...
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Comparison of backscattered sea bottom echo modelling in the acoustic pressure domain and in the intensity domain
PublikacjaPrzedstawiono dwie metody modelowania rozpraszania wstecznego na dnie morskim: modelowania ciśnienia akustycznego opartego na aproksymacji Kirchhoffa oraz modelowania natężenia echa przy założeniu dominacji rozpraszania niekoherentnego. Porównano i przedyskutowano wyniki w odniesieniu do problemu poszukiwania jak najwłaściwszego opisu zjawiska rozpraszania sygnału akustycznego na dnie.
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Passive layer cracking studies performed on A95056 Aluminum Alloy by DEIS and acoustic emission
PublikacjaZbadano proces pękania warstwy pasywnej na stopie aluminium A95056 w warunkach zmiennych naprężeń rozciągających i polaryzacji anodowej z wykorzystaniem techniki DEIS oraz emisji akustycznej (AE), jako metody porównawczej. Określono elektrochemiczne i mechaniczne przyczyny badanego procesu. Wyznaczono progową (krytyczną) wartość naprężeń, przy których zarejestrowano proces pękania warstwy pasywnej na badanym stopie aluminium. Badanemu...
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Shaping the SPL Spectra of the Acoustic Noise Emitted by Inverter-Fed Indu- ction Motors
PublikacjaW artykule przedstawiono nowe podejście do zmniejszania wpływu właściwości mechanicznych maszyny na emitowany przez nią hałas akustyczny. Dokonano identyfikacji mechanicznych rezonansów maszyny wykorzystując modulację RPWM z losowym wyborem częstotliwości nośnej oraz modulację sigma delta, dla której otrzymano relatywnie płaskie widmo prądu. Skonstruowano na tej podstawie funkcję gęstości prawdopodobieństwa wyboru częstotliwości...
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Optimizing acoustic field intesity algorithms using the sound ray surface density method.
PublikacjaW artykule przedstawiono zagadnienia optymalizacji algorytmów komputerowych obliczeń rozkładów natężeń pola akustycznego w akwenie w zależności od za- mierzonych warunków hydrologicznych pod kątem skrócenia czasu obliczń.
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Complementary study with magnetic and acoustic techniques of A336 steel damage state due to creep
PublikacjaBadano możliwość detekcji w sposób nieniszczący zmian w mikrostrukturze stali A336 poddanej próbie pełzania. Testowano dwie magnetyczne techniki (klasyczny efekt Barkhausena i emisję magnetoakustyczną) oraz dwie nowe techniki ultradźwiękowe (pomiar współczynnika elasto-akustycznego oraz dwójłomność akustyczną). Wykazano, iż wyniki badań akustycznych są komplementarne do wyników badań magnetycznych.
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Thermal self-action effects for acoustic beams containing fronts in a Maxwell relaxing fluid
PublikacjaThis paper examines the thermal self-action of acoustic beams in a Maxwell relaxing fluid. This type of thermal self-action differs from that in a Newtonian fluid and behaves differently depending on a ratio of sound period and time of thermodynamic relaxation. The self-action which relates to sound beams containing shock fronts is also discussed. In addition, stationary and non-stationary types of self-action are considered.
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Measurement of Seafloor Acoustic Backscatter Angular Dependence at 150 kHz Using a Multibeam Echosounder
PublikacjaAcoustic seafloor measurements with multibeam echosounders (MBESs) are currently often used for submarine habitat mapping, but the MBESs are usually not acoustically calibrated for backscattering strength (BBS) and cannot be used to infer absolute seafloor angular dependence. We present a study outlining the calibration and showing absolute backscattering strength values measured at a frequency of 150 kHz at around 10–20 m water...
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A Numerical Study on Baseline-Free Damage Detection Using Frequency Steerable Acoustic Transducers
PublikacjaIn structural health monitoring (SHM) a considerable amount of damage detection algorithms based on guided waves (GW) have been developed. Most of them rely on extensive transducer networks, besides preliminary reference measurements of the structures. This originated a growing demand for hardware simplification and cost reduction of the wave-based SHM methods, driving the conception of new solutions enabling both: the reduction...
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Adaptive identification of sparse underwater acoustic channels with a mix of static and time-varying parameters
PublikacjaWe consider identification of sparse linear systems with a mix of static and time-varying parameters. Such systems are typical in underwater acoustics (UWA), for instance, in applications requiring identi- fication of the acoustic channel, such as UWA communications, navigation and continuous-wave sonar. The recently proposed fast local basis function (fLBF) algorithm provides high performance when identi- fying time-varying systems....
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Pursuing Analytically the Influence of Hearing Aid Use on Auditory Perception in Various Acoustic Situations
PublikacjaThe paper presents the development of a method for assessing auditory perception and the effectiveness of applying hearing aids for hard-of-hearing people during short-term (up to 7 days) and longer-term (up to 3 months) use. The method consists of a survey based on the APHAB questionnaire. Additional criteria such as the degree of hearing loss, technological level of hearing aids used, as well as the user experience are taken...
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3D Sound Intensity Measurement Around Organ Pipes Using Acoustic Vector Sensors
PublikacjaThe aim of the presented paper was to obtain and visualize sound intensity distribution of radiated acoustic energy around the organ pipes. The experimental setup consisted of the multichannel acoustic vector sensor and the specialized Cartesian robot. Measurements were performed in free field with spatial resolution of 0.1 [m]. Two organ pipes, i.e. wooden and metal were measured during the ex-periment. The organ pipes were activated...
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Application of acoustic emission for detection of fatigue microdemage in main and crank bearings for diesel engines
PublikacjaThe article presents reasons for applying the acoustic emission (AE) to detect fatigue microdamage in main bearings and crank bearings of ship main engines. Problem of determination of the fatigue life for slide bearing bushes was characterized in general. There were demonstrated properties of the objects of research, which were bushings made of the MB58 alloy, as well as an overall description of the research. It was shown that...
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Acoustic journal bearing – Performance under various load and speed conditions speed conditions
PublikacjaThe paper presents results of experimental testing aiming at finding out what effect system of piezo-electric actuators (PZTs)attached to an aerodynamic journal bearing has on the magnitude of shaft's motion within the bearing operating at specified speed and load. The results clearly demonstrate effectiveness of PZTs in mitigating the shaft's motion thus contributing to the increased stability of the bearing. This stabilizing...
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1D convolutional context-aware architectures for acoustic sensing and recognition of passing vehicle type
PublikacjaA network architecture that may be employed to sensing and recognition of a type of vehicle on the basis of audio recordings made in the proximity of a road is proposed in the paper. The analyzed road traffic consists of both passenger cars and heavier vehicles. Excerpts from recordings that do not contain vehicles passing sounds are also taken into account and marked as ones containing silence....
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Stationary underwater channel experiment: Acoustic measurements and characteristics in the Bornholm area for model validations
PublikacjaThe underwater acoustical channel is time-variant, and even on small time scales there is often existing no ‘acoustical frozen ocean’. Popular is the use of WSSUS-channel transmission modeling (Wide-Sense Stationary Uncorrelated Scattering) for the stochastic description of bandpass signals in GSM mobile phones with moving participants; since this results in a halved number of model parameters. For underwater sound applications...
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Bimodal classification of English allophones employing acoustic speech signal and facial motion capture
PublikacjaA method for automatic transcription of English speech into International Phonetic Alphabet (IPA) system is developed and studied. The principal objective of the study is to evaluate to what extent the visual data related to lip reading can enhance recognition accuracy of the transcription of English consonantal and vocalic allophones. To this end, motion capture markers were placed on the faces of seven speakers to obtain lip...
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Acoustics of concert hall at academy of music in Gdańsk, project and realization
PublikacjaArtykuł opisuje właściwości akustyczne sali koncertowej Akademii Muzycznej w Gdańsku, ukończonej w roku 2007. Przedstawiono zalecenia akustyczne do projektu architektonicznego w zakresie akustyki budowlanej i akustyki wnętrz. Podano wyniki pomiarów akustycznych na kolejnych etapach realizacji obiektu.
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Interaction of modes in nonlinear acoustics: theory and applications to pulse dynamics.
PublikacjaOgólna teoria oddziaływania modów hydrodynamicznych opiera się na wyprowadzeniu równań różniczkowych nieliniowych. Mody rozumiane są tu jako wektory własnych układów praw zachowań hydrodynamicznych. Rozpatrywano zjawiska towarzyszące fali akustycznej w przepływie lepkim nieliniowym. Uwzględniono płyny w każdym fizycznym równaniu stanu.
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IMPACT OF CAUSTICS ON ACOUSTICS OF WHISPERING GROTTOES IN THE OLIWA PARK IN GDAŃSK
PublikacjaIn the paper, caustics are discussed as ordered forms of focus broadening occurring in concave mirrors. An example of caustics created by the reflection of the light from the concave mirror is shown. Against this background, the possibility to observe caustics in rooms is pointed out. Special emphasis is put on large rooms of historic character, as such interiors frequently include acoustic mirrors in the form of arched vaults...
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Recent developments in automatic classification of musical instruments. W:[CD-ROM] Collected papers. First Pan-American/Iberian Meeting on Acoustics. 144 Meeting of the Acoustical Society of America. III Iberoamerican Cong- ress of Acoustics. 9o Mexican Congress of Acoustics. Cancun, Q. R. Mxico, 2-6 Dec. 2002. [B.m.:ASA]**2002 paper 2aMU4, 7 s. 6 rys. 1 tab. bibliogr. 21 poz. Automatyczne rozpoznawanie muzyki - przykłady eksperymentów.
PublikacjaW referacie dokonano przeglądu aktualnego stanu badań w dziedzinie automaty-cznego rozpoznawania muzyki. Przedstawiono też eksperymenty prowadzone aktu-alnie w Katedrze Dźwięku i Obrazu PG. Prace te dotyczyły rozpoznawania klasinstrumentów muzycznych i separacji duetów muzycznych. Pokazano przykładowewyniki i przedstawiono projekt prac do zrealizowania w przyszłych ekspery-mentach.
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An approach to determining tinnitus acoustical characteristic
PublikacjaFor many treatment methods, accurate estimation of Tinnitus(ringing in ears) concerning sound type, level, and bandwidth or frequency is inevitable. The proposed way of obtaining Tinnitus parameters is described in this paper. The method employs sound synthesis, aimed at obtaining sound which is closest to perceived Tinnitus. The proposed method assumes running a designed application on a multimedia PC provided with a special graphical...
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Adaptacja akustyczna pomieszczenia wykładowego - studium przypadku
PublikacjaW niniejszej pracy przedstawiono analizę rozkładu pola akustycznego sali wykładowej znajdującej się w budynku Wydziału Elektroniki i Telekomunikacji Politechniki Gdańskiej. Badania przeprowadzono metodą pomiarową oraz symulacyjną z wykorzystaniem programu Odeon. Wybór parametrów oceny akustyki wnętrz sugerowany jest wymaganiami stawianymi pomieszczeniom lekcyjnym z zaznaczeniem multimedialnego charakteru wykładów prowadzonych...
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The use of Acoustic Emission to identification damages bearings the main and crank engines about the automatic ignition
PublikacjaThe article describes the laboratory tests, which make the first stage of the study concerning the use of the AE method to determine the technical state of the slide bearings in engines with self-ignition. The aim of the present tests was to compare the recorded signals in relation to the technical state of the material of the bearing bush and to check the possibility of using the AE method in determining the transition moment...
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Anomalous pressure dependence of acoustic phonons of AgGaSe2 investigated by inelastic neutron scattering to 4.3 GPa
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Akustyczny obraz słowa na tle mowy etnicznej [The acoustic image of ethnic speech words]
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Impact of Tensile and Compressive Stress on Classical and Acoustic Barkhausen Effects in Grain-Oriented Electrical Steel
PublikacjaIn this paper, we present the results of the investigation of impact of tensile and compressive stress on the classical Barkhausen effect, magnetoacoustic emission (MAE) signal properties, and B(H) hysteresis loops for grain-oriented (GO) electrical steel. Samples have been glued to a nonmagnetic steel bar and stressed within elastic range (±800 μdef) by means of four-point bending method. The samples were cut out in two directions...
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Enhanced voice user interface employing spatial filtration of signals from acoustic vector sensor
PublikacjaSpatial filtration of sound is introduced to enhance speech recognition accuracy in noisy conditions. An acoustic vector sensor (AVS) is employed. The signals from the AVS probe are processed in order to attenuate the surrounding noise. As a result the signal to noise ratio is increased. An experiment is featured in which speech signals are disturbed by babble noise. The signals before and after spatial filtration are processed...
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Robust identification of glass breaks acoustic signals based on Wavelet transformation and Rock Solid Attributes.
PublikacjaStosowane w systemach alarmowych współczesne metody detekcji zbicia szyby, wykorzystują zwykle analizę sygnałów akustycznych towarzyszących temu procesowi. Podstawową metodą identyfikacji jest detekcja kilku charakterystycznych częstotliwości, niestety takie podejście wprowadza możliwość zafałszowania wyniku detekcji przez sygnały fałszywe, które mają zbliżaną charakterystykę widmową. Znacznie lepsze rezultaty osiągnąć można stosując...
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Analysis of Roughness, the Material Removal Rate, and the Acoustic Emission Signal Obtained in Flat Grinding Processes
PublikacjaIn this work, the analysis of the acoustic emission (AE) signal in grinding processes is addressed. The proposed analysis method decomposes the acoustic signal into three frequency ranges. The total energy of each range is determined, as well as the highest frequency. Different grinding experiments were carried out, according to a full factorial design of experiments (DOE), in which feed speed, depth of cut, and transversal step...
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Failure characterisation of sandwich beams using integrated acoustic emission and digital image correlation techniques
PublikacjaThe paper presents the experimental study of the failure behaviour of sandwich beams subjected to bending. The samples examined are sandwich beams made of polyethylene terephthalate foam core and glass fibre-reinforced polymer laminate face sheets. In a series of experiments, it has been proposed to integrate diagnostic techniques with acoustic emission and digital image correlation to accurately track the cracking process on the...
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Application of inserts for suppression of coupled dynamic-acoustic effects during confined granular flow in silos
PublikacjaArtykuł omawia sposoby redukcji efektów dynamiczno-akustycznych w silosach. Do redukcji zastosowano różne wkładki. Zbadano wpływ kształtu i liczby wkładek w doświadczeniach. Na podstawie wyników doświadczalnych opracowano metodę redukcji efektów dynamiczno-akustycznych w dużych stalowych silosach.
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Microcracking monitoring and damage detection of graphene nanoplatelets-cement composites based on acoustic emission technology
PublikacjaThis study aims to identify the micro-cracking pattern and structural applications of cement composites replaced with 0 wt%, 0.04 wt%, and 0.08 wt% contents of graphene nanoplatelets (GNPs) over cement weight through acoustic emission (AE) monitoring under mechanical degradation. The ultraviolet-visible spectroscopy (UV–vis) results showed that at 60 min sonication period, GNP-4 showed maximum absorbance rate of 16.15% compared...
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Simulation of Direct-Sequence Spread Spectrum Data Transmission System for Reliable Underwater Acoustic Communications
PublikacjaUnderwater acoustic communication (UAC) system designers tend to transmit as much information as possible, per unit of time, at as low as possible error rate. It is a particularly difficult task in a shallow underwater channel in which the signal suffers from strong time dispersion due to multipath propagation and refraction phenomena. The direct-sequence spread spectrum technique (DSSS) applied successfully in the latest standards...
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Estimating Traffic Intensity Employing Passive Acoustic Radar and Enhanced Microwave Doppler Radar Sensor
PublikacjaInnovative road signs that can autonomously display the speed limit in cases where the trac situation requires it are under development. The autonomous road sign contains many types of sensors, of which the subject of interest in this article is the Doppler sensor that we have improved and the constructed and calibrated acoustic probe. An algorithm for performing vehicle detection and tracking, as well as vehicle speed measurement,...
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Study of probe signal bandwidth influence on estimation of coherence bandwidth for underwater acoustic communication channel
PublikacjaA signal transmitted in a shallow Underwater Acoustic Communication (UAC) channel suffers from time dispersion due to the multipath propagation and the refraction phenomena. This causes intersymbol interference of the received signal and frequency-selective fading observed in its spectrum. Coherence bandwidth is one of the key transmission parameters used for designing the physical layer of a data transmission system to minimise...