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Wyniki wyszukiwania dla: ACOUSTIC CAVITATION
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Designing acoustic scattering elements using machine learning methods
PublikacjaIn the process of the design and correction of room acoustic properties, it is often necessary to select the appropriate type of acoustic treatment devices and make decisions regarding their size, geometry, and location of the devices inside the room under the treatment process. The goal of this doctoral dissertation is to develop and validate a mathematical model that allows predicting the effects of the application of the scattering...
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Machine learning applied to acoustic-based road traffic monitoring
PublikacjaThe motivation behind this study lies in adapting acoustic noise monitoring systems for road traffic monitoring for driver’s safety. Such a system should recognize a vehicle type and weather-related pavement conditions based on the audio level measurement. The study presents the effectiveness of the selected machine learning algorithms in acoustic-based road traffic monitoring. Bases of the operation of the acoustic road traffic...
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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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Machine learning applied to acoustic-based road traffic monitoring
PublikacjaThe motivation behind this study lies in adapting acoustic noise monitoring systems for road traffic monitoring for driver’s safety. Such a system should recognize a vehicle type and weather-related pavement conditions based on the audio level measurement. The study presents the effectiveness of the selected machine learning algorithms in acoustic-based road traffic monitoring. Bases of the operation of the acoustic road traffic...
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Efficiency of acoustic heating produced in the thermoviscous flow of a fluid with relaxation
PublikacjaInstantaneous acoustic heating of a fluid with thermodynamic relaxation is the subject of investigation. Among others, viscoelastic biological media described by the Maxwell model of the viscous stress tensor, belong to this type of fluid. 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...
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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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Numerical modeling of sound intensity distributions around acoustic transducer
PublikacjaThe aim of this research study is to measure, simulate and compare sound intensity distribution generated by the acoustic transducers of the loudspeaker. The comparison of the gathered data allows for validating the numerical model of the acoustic radiation. An accurate model of a sound source is necessary in mathematical modeling of the sound field distribution near the scattering obstacles. An example of such obstacle is a human...
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The effect of tire aging on acoustic performance of CPX reference tires
PublikacjaReduction of tire/road noise is one of the biggest environmental challenges of road traffic. To reduce that noise it is necessary to perform acoustic measurements on the base of wellproven standard procedures. One method of measurements that is in common use, namely the Close Proximity Method (CPX), is described in standard ISO-DIS 11819-2. As this method is used to classify road surfaces regarding their influence on vehicle noise,...
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Shallow-Water Acoustic Communications in Strong Multipath Propagation Conditions
PublikacjaA phenomenon that has a strong impact on signal transmission conditions in Underwater Acoustic Communication (UAC) systems is multipath propagation. As a result of multipath propagation, the transmitted signal undergoes time dispersion which results in inter-symbol interference observed on the receiving side. Time dispersion is large, especially in horizontal channels in shallow waters which significantly limits the transmission...
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Acoustic radiation force and streaming caused by non periodic acousticsource.
PublikacjaTeoria i obliczenia numeryczne przepływu rotacyjnego (''streamingu'') towarzyszącemu fali akustycznej w przepływach lepkich nieliniowych. Fala wywołująca może być nieokresowa: impulsowa lub paczka falowa itd. Przykład pojedynczego pulsu rozpatrywany. Ilustracje delikatnej struktury czasowej powstania fal rotacyjnych przedstawione na rysunkach.
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Liquid water. Analytical equation of state and acoustic parameters evaluation.
PublikacjaRównanie stanu dla ciekłej wody zaproponowane przez Jefferya - Austina zastosowano do obliczeń prędkości dźwięku oraz parametru nieliniowości B/A. Parametry akustyczne są porównywane z danymi doświadczalnymi.
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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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A novel approach to bottom scattering using a narrow acoustic beam.
PublikacjaPrzedstawiono model opisujący w prosty sposób rozpraszanie sygnału akustycznego na dnie morskim jako filtr liniowy z odpowiedzią impulsową o zmieniającej się w czasie chwilowej dominującej częstotliwości. Przedyskutowano pasujący do tego modelu przypadek zbioru punktowych rozpraszaczy równomiernie rozmieszczonych na powierzchni dna, w tym wpływ takich parametrów jak głębokość oraz odległość pomiędzy rozpraszaczami.
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Projekt systemu nagłośnieniowego z wykorzystaniem oprogramowania CATT-Acoustic.
PublikacjaW niniejszej pracy zawarto projekt modelu akustycznego sali audytoryjnej oraz weryfikację charakterystyk pola akustycznego tego modelu w oparciu o program CATT-Acoustic. W pracy przedstawiono również projekt systemu nagłośnienia modelowanej sali audytoryjnej, który z punktu widzenia właściwości akustycznych powinien zapewnić jak najlepszą zrozumiałość mowy. Dokonano analizy porównawczej pola akustycznego bez oraz z zaimplementowanym...
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Distributed Evolutionary Algorithm for Path Planning in Navigation Situation
PublikacjaThis article presents the use of a multi-population distributed evolutionary algorithm for path planning in navigation situation. The algorithm used is with partially exchanged population and migration between independently evolving populations. In this paper a comparison between a multi-population and a classic single-population algorithm takes place. The impact on the ultimate solution has been researched. It was shown that using...
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Remote Spatial Database Access in the Navigation System for the Blind
PublikacjaThe article presents the problem of a database access in the navigation systems. The authors were among the main creators of the prototype navigation system for the blind - “Voice Maps”. In the implemented prototype only exemplary, limited spatial data were used, therefore they could be stored in the mobile device’s memory without any difficulties. Currently the aforementioned system is being prepared for commercialization - the...
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Methods of navigation in the mobile application supporting movement of the blind
PublikacjaThis paper presents conclusions from the last development phase of the “Voice Maps” project. Authors specify newly found available options for navigation in affordable system for the blind with all their related aspects. System uses dedicated geographical data, built-in smartphone GPS receivers and DGPS external device in order to assist blind users in their everyday travelling. Authors also discuss new methods to improve positioning...
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DETERMINANTS OF INLAND NAVIGATION ON THE VISTULA FROM WARSAW TO GDAŃSK
PublikacjaWaterborne transport is the cheapest, the safest and the least harmful to the natural environment. Restoring regular waterway cargo transport will require revitalisation of the existing trans-shipment and logistics infrastructure for commercial inland ports and building new. Transport policy makers must remember that waterborne transport is the most ecological type of transport. It produces only 10% of the gases emitted to the...
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Inexpensive Helical Antenna for Global Navigation Satellite Systems
PublikacjaZaprezentowane zostały wyniki badań teoretycznych oraz eksperymentalnych niskobudżetowej anteny na pasmo L. Wyjściowa geometria struktury została obliczona na podstawie ogólnych wzorów. Efekt przesunięcia częstotliwości wywołany przez użycie rdzenia PU został również uwzględniony. Równolegle przeprowadzono badania wrażliwości parametrów anteny na proces produkcji. Zaprojektowano i wykonano układ dopasowania impedancyjnego. W paśmie...
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A risk analysis of winter navigation in Finnish sea areas
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Dynamic interaction of the cavitating propeller tip vortex with the rudder
PublikacjaPraca przedstawia model teoretyczny i obliczeniowy dynamicznego oddziaływania kawitującego wiru wierzchołkowego śruby okrętowej z płetwą sterową. W wyniku oddziaływania zmienia się geometria wiru, powodując generowanie wysokich pulsacji ciśnienia w otaczającej wodzie i na kadłubie okrętu. Wyniki obliczeń skonfrontowano z rezultatami pomiarów laboratoryjnych na modelach. Pokazano praktyczną przydatność modelu obliczeniowego do projektowania...
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An Integrated Approach to an Assessment of Bottlenecks for Navigation on Riverine Waterways
PublikacjaWater transport, both sea and inland, is the cheapest, least invasive, and safest option for non-standard loads; hence, it is important to increase the percentage share of inland waterway transport on the rivers of Central and Eastern Europe. Transporting cargo is particularly difficult on shallow waterways because rivers overloaded with sediment determine the vertical parameters on inland waterways. A ship’s safe manoeuvrability...
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A VISION-BASED UNMANNED AERIAL VEHICLE NAVIGATION METHOD
PublikacjaThe satellite navigation systems are the main position sources for unmanned aerial vehicles (UAVs). This fact limits the area of UAVs operation to the places where radio signals is visible for a satellite navigation system receiver, mounted on the vehicle-outdoor navigation. Closed spaced are unavailable for vehicles which navigation is based on global satellite navigation systems (GNSS). Miniature UAV (MiniUAV) is able to operate...
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Matching trajectory of a person to a map in inertial navigation system
PublikacjaPaper describes the method of matching, to a map, trajectories of a person walking indoors, obtained from inertial navigation module. General principle of matching algorithm based on particle filtering is presented. Method of detecting particle collisions is described as well. The last chapter provides test results of map matching related to a true trajectory.
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Semi complex navigation with an active optical gesture sensor
PublikacjaThis paper presents the methods of diversified touchless interactions between a user and a mobile platform utilizing the optical gesture sensor. The sensor uses 8 photodiodes to measure the reflected light in the active mode (using embedded LEDs) or it measures shadows caused by fingers in the passive mode. Several algorithms were implemented: automatic mode switching, adaptive illumination level compensation, resolution improvements...
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Has EGNOS its own place in maritime navigation?
PublikacjaGNSS (in fact it usually means GPS) is at the moment the fundamental means of positioning for any variants of navigation. However some attributes of it can be not sufficient for every users or in some tasks, so there are any cases when this system needs support. From the mariner point of view pure GPS properties perfectly fulfils expectations of sailors at the open sea, however there are lot of cases, when accuracy of the system...
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TDOA Navigation Using CDMA2000 Signals – Experimental Results
PublikacjaThis paper presents results of an experiments on the possibility to estimate position of a CDMA2000 receiver on the basis of TDOA measurements. The hardware and software structure of a navigation receiver used during investigation is briefly described with focus on drawbacks and limitations. The main part of this paper contains basic information about CDMA2000 network in northern Poland, which signals were recorded during tests...
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Perfecting the Maritime Navigation information services of the European Union
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Modelling processes for Polish civil aviation market
PublikacjaThe present , paper is the first step in research of Polish civil aviation market, focusing on the area of civil, legacy airlines. First, the market is described with its players, current conditions and its main problems. Next, the tools which are currently used for the prognosis processes are presented. Finally, the idea of a new model (fuzzy model) for the process of prognosis is presented.
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THE CASE OF MANAGEMENT CONCEPTS IN CIVIL AVIATION BUSINESS.
PublikacjaThe article presents the changes in management concepts used in civil aviation business in last 25 years. There is a need to make prognosis and support decision-making processes with different models but each model is adapted to current management concept. This article will present the changes and possible future trends in management concepts with the description of strengths and weaknesses of each of them. These might be used...
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Evaluation of cavitation erosion-corrosion degradation of mild steel by means of Dynamic Impedance Spectroscopy in galvanostatic mode
PublikacjaPrzedstawiono wyniki badań degradacji stali węglowych na skutek oddziaływania erozji-korozji kawitacyjnej. Do analizy wykorzystano technikę Dynamicznej Elektrochemicznej Spektroskopii Impedancyjnej w trybie galwanostatycznym, bliżej odwzrorowującym warunki naturalne. Do oceny stopnia degradacji posłużyły również funkcja ubytku masy MDPR oraz obrazy mikroskopowe SEM. Potwierdzono wpływ łączonej degradacji erozyjno-korozyjnej na...
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Evaluation of cavitation erosion–corrosion degradation of mild steel by means of dynamic impedance spectroscopy in galvanostatic mode
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A study of cavitation erosion resistance of an ion nitrided titanium alloy by means of the vibration and rotating disk methods
PublikacjaIn this work, a comparative analysis of the cavitation erosion resistance of the Ti– 6.7Al–2.5Mo–1.8Cr–0.5Fe–0.25Si alloy (known as brand VT3-1) before and after lowtemperature ion nitriding is carried out. Two test methods were applied, using vibrative (ASTM G-32) and rotating disk rigs, respectively. The kinetic dependences of the erosive destruction of samples of titanium alloy VT3-1 in the initial state, after ion nitriding...
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Ultrafast degradation of brilliant cresyl blue under hydrodynamic cavitation based advanced oxidation processes (AOPs)
PublikacjaThe study highlights effectiveness of hydrodynamic cavitation (HC) in the degradation of effluents polluted by Brilliant Cresyl Blue (BCB) dye. Optimal process parameters were cavitation number 0.27, inlet pressure 1.70 bar, temperature 20 °C and pH 7. The efficiency of HC was investigated in combination with other advanced oxidation processes, including the addition of external oxidants (hydrogen peroxide, ozone, and sodium persulfate)...
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Modeling of acoustics of hearing aid earmold systems
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Accoustic verification of onomatopoeic sets in contrastive approach
PublikacjaPraca relacjonuje efekty prób wykorzystania technik cyfrowego przetwarzania sygnału mowy dla zaspokojenia specyficznych potrzeb nauk humanistycznych, które, ograniczając się wyłącznie do tra-dycyjnie stosowanego warsztatu badawczego, napotykają współcześnie na bariery znacznie blokują-ce oczekiwany postęp. Omówiono proces badawczy, który służyć ma językoznawcom dokonującym porównań wyrażeń dźwiękonaśladowczych odnajdywanych w odmiennych...
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Impact of the glazed roof on acoustics of historic interiors
PublikacjaThe paper discusses the adverse acoustic phenomena occurring in the semi-open interiors (courtyards, yards) covered with a glass roof. Particularly negative is the rever-beration noise, which leads to the degradation of the utility functions of the resulting spaces. It involves the drastically reducing the intelligibility of speech, loss of natural sounding of music, problems with the sound system, as well as disturbances in the...
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Magnetic properties of BiFeO3micro-cubes synthesized by microwave agitation
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Thermal self-action effects of acoustic beam in a vibrationally relaxing gas
PublikacjaThermal self-action of acoustic beam in a molecular gas with excited internal degrees of molecules’ freedom, is studied. This kind of thermal self-action differs from that in a Newtonian fluid. Heating or cooling of a medium takes place due to transfer of internal vibrational energy. Equilibrium and non-equilibrium gases, which may be acoustically active, are considered. A beam in an acoustically active gas is self-focusing unlike...
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Self-refraction of acoustic pulses with shock fronts in some nonequilibrium media
PublikacjaThe nonlinear self-refraction of acoustic pulsed beams, which include shock fronts, is studied. The medium of sound propagation is a gas where thermodynamically nonequilibrium processes take place, such as exothermic chemical reaction or excitation of vibrational degrees of a molecule’s freedom. Comparative analysis of the features of sound propagation over gases where pure nonlinear attenuation of the shock wave occurs, and gases...
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Application of acoustic emission metod for measurement of joint gap and cartilage surfaces
PublikacjaW artykule przedstawiono zastosowanie emisji akustycznej do lokalizacji wczesnych uszkodzeń stawu biodrowego lub kolanowego człowieka. Ponadto metoda ta służy do pomiaru wysokości szczeliny stawu oraz struktury geometrycznej powierzchni chrząstki stawowej. Jest to metoda nieinwazyjna. Pomiary metodą emisji akustycznej stosujemy na ogół w materiałach, w których energia sprężysta zmienia się nagle. Takie zmiany energii mogą być...
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Weakly nonlinear dynamics of short acoustic waves in exponentially stratified gas
PublikacjaRozpatruje się dynamika krótkich (w porównywaniu z charakterystyczną skalą zmiany gęstości gazu atmosferycznego) fal akustycznych. Wyprowadzone nowe równanie ewolucyjne, które uwzględnia dyspersję i nieliniowy charakter propagacji tych fal. Porównuje sie liniowa i nieliniowa dynamika. Ilustracje propagacji, numeryczne wyliczione na podstawie nowych wzorów, są przedstawione. Indexed and abstracted (from vol. 32(1) 2007) in Science...
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Dynamic computation of acoustic field distribution in the city area employing a supercomputer
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The effect of pumpkin flour on quality and acoustic properties of extruded corn snacks
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An Experimental Study on the Effect of Temperature on Acoustic Emission Characteristics in Metallic Structures
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High resolution optical and acoustic remote sensing datasets of the Puck Lagoon
PublikacjaThe very shallow marine basin of Puck Lagoon in the southern Baltic Sea, on the Northern coast of Poland, hosts valuable benthic habitats and cultural heritage sites. These include, among others, protected Zostera marina meadows, one of the Baltic’s major medieval harbours, a ship graveyard, and likely other submerged features that are yet to be discovered. Prior to this project, no comprehensive high-resolution remote sensing...
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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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Application of the corrosion tester in corrosion tests using the acoustic emission method.
PublikacjaThe article presents an innovative method of corrosion tests using the acoustic emission method and the corrosion tester. The problem of corrosion occurring in ballast tanks and tanks carrying petroleum products is discussed. The acoustic method is presented which, due to the use of a unique corrosion tester, is used to monitor the course of corrosion processes in steel. The principle of operation of the corrosion tester, its construction...
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Thermal Self-Action of Acoustic Beams Containing Several Shock Fronts
PublikacjaThermal self-action of an acoustic beam with one discontinuity or several shock fronts is studied in a Newtonian fluid. The stationary self-action of a single sawtooth wave with discontinuity (or some integer number of these waves), symmetric or asymmetric, is considered in the cases of self-focusing and self- defocusing media. The results are compared with the non-stationary thermal self-action of the periodic sound. Thermal self-action...
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Comparison of Acoustic and Visual Voice Activity Detection for Noisy Speech Recognition
PublikacjaThe problem of accurate differentiating between the speaker utterance and the noise parts in a speech signal is considered. The influence of utilizing a voice activity detection in speech signals on the accuracy of the automatic speech recognition (ASR) system is presented. The examined methods of voice activity detection are based on acoustic and visual modalities. The problem of detecting the voice activity in clean and noisy...