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In this paper, we present a novel approach for the sensing of erosive cavitation phenomena in underwater facilities. Cavitation phenomena are known for their destructive capacity of underwater structures and are caused by the pressure decreasing followed by an implosion when the cavitation bubbles find an adverse pressure gradient. Conventional cavitation detection techniques are based on passive...
The underwater object imaging is an important task for the surveillance and monitoring of underwater environment in a non-intrusive manner. The acoustic methods have been proved to be very powerful for the detection and localization of underwater objects. This paper proposes a new method for object imaging based on an acoustic system that uses multiple elements. The image is obtained using two main...
Time-frequency analysis is naturally the way of characterization of non-stationary signals. One fundamental parameter of the any-non-stationary is the Instantaneous Frequency Law of its components. The Instantaneous Frequency Law (IFL) estimation is usually subject of tracking in time-frequency domain, especially in the case of complex time-frequency structures. Using the concept of phase diagram...
The paper presents a different approach based on an active acoustic system for the characterization of a vortex generating cavitation phenomenon. In the present work, the experiment was carried out in a reduced scale facility. The flow rate of the hydraulic system was varied and, when the flow became stable, the acoustic active system was started. The system is based on two ultrasonic transceivers...
From twenty years we promote the idea that engineering's systems (and not only!) are nonlinear ones and usually can have chaotically behaviors and their associated processes need special studies' methods. In this paper we present two directions from our research: cryptography based on chaos and a new method to analyze signals from nonlinear dynamical systems.
The paper presents an acoustic signal processing approach for the surveillance of a water pipe and the characterization of the water hammer effect. The experiment is based on ultrasonic transceivers and the validation is made with pressure sensors. The major objective is to quantify the pressure variation into the pipe using a non-intrusive method. Therefore, the speed of the transient was determined...
This paper presents several methods applied for the detection and localization of electrical arcs measured while survelling photovoltaic power systems. Firstly, we proposed the use of energy detectors for transients (spectrogram and wavelet) and compared them with statistical methods (Maximum Likelihood Estimation (MLE)), classical signal processing methods (Matched Filter, Zero Crossing), but not...
This paper proposes a new method for detection of the vortex presence in fluid flow based on an active acoustic system. The experiment that validates the theory was done on a reduced scale facility using ultrasonic transceivers. The main objective was to highlight the effect of a cavitation vortex on an applied wide band signal. In order to accomplish that, the Recurrence Plot Analysis (RPA) was investigated...
The fetal heart rate (FHR) is a fundamental tool for clinical monitoring, when investigating the wellbeing of the fetus. The detection of the QRS complex of the fetal electrocardiogram using the abdominal signal enables the non-invasive evaluation of the FHR. There are many clinical causes for FHR variability, but a slight variance indicates a good evolution of the pregnancy. The current study evaluates...
This paper highlights the main results of our research in the field of recurrence plot analysis in the last five years. It briefly discusses results in the study of the method itself, as well as in some applications of it, i.e. characterization of speech signals, detection and localization of partial discharges in electric cables, representation of transient signals, estimation of signal parameters,...
The detection and characterization of burst signals are challenging tasks for time-frequency analysis, due to their very short duration. This paper investigates in this context the recurrence plot analysis (RPA) method, from which it derives the vector samples processing (VeSP) concept. The paper shows that VeSP is a generic framework that unifies signal processing concepts like histogram and autocorrelation,...
In this paper we approach the challenges of partial discharges (PD) detection in high voltage cables using signal processing techniques based on time frequency methods combined with Recurrence Plot Analysis (RPA) and high order spectrum analysis (HOSA). Detection of PD poses many problems in terms of speed of calculation, selection criteria and multitude of causes which lead to the occurrence of PD...
Burst-type signals constitute an important class of transient signals, being used especially in the investigation of various physical environments by electric or acoustic means. An important issue in the analysis of this type of signals is their detection in time. In this paper, we propose a detection method that is based on the histogram of the phase space distributed over time. The method consists...
One of the most challenging applications of time-frequency representations deals with the analysis of the signal issued from natural environment. Recently, the interest for passive underwater context increased, basically due to the rich information carried out by the natural signals. Taken into account the non-linear multi-component time-frequency behavior of such signals, their analysis is a complex...
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