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Constanţa, Romania

George Z.,Maritime University of Constanta
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2012

The success of terrestrial wireless sensor networks in monitoring various phenomena caused an increased interest to develop underwater sensor networks by the underwater acoustics community. These networks are based on underwater acoustic modems for real-time data transmission. The high cost and fixed architecture of these devises makes it impossible to implement dense wireless sensor networks adapted to the environment. We propose an adaptive architecture for a low cost underwater acoustic modem. Designing such a modem with adaptable parameters is determined by the zonal variability of the underwater channel. This article presents the results of a frequency dependent simulation for a particular underwater channel in the Black Sea for which we determined the distance dependent impulse response. The simulation results reinforce the idea of variability of the transmission channel and support the idea of designing an adaptive underwater acoustic modem. Underwater acoustic modem, frequency dependent simulation, underwater wireless sensor network, underwater acoustic channel. © 2012 SPIE. Source


Deleanu D.N.,Maritime University of Constanta
ECCOMAS 2012 - European Congress on Computational Methods in Applied Sciences and Engineering, e-Book Full Papers | Year: 2012

Investigating a discrete or continuous dynamical system, one of the most important challenges is to distinguish between its ordered or chaotic orbits. This distinction is of great interest because in the case of ordered motions we have predictability whereas for chaotic motions we are unable to predict the time evolution of the dynamical system after a short time period. After we have studied a significant number of papers concerning this subject, we would try in the present paper to emphasize the strong and weak points of three recent indicators of chaos and order, namely Fast Lyapunov Indicator (FLI), Smaller Alignment Indices (SALI), and the Dynamic Lyapunov Indicator (DLI). For this, we first recall the definitions of FLI, SALI and DLI. Then, we demonstrate the usefulness of the above-mentioned indicators by applying them to the Tinkerbell map, the Lorentz BD map, the Rucklidge oscillator and the double-pendulum system. The main observations of our study refer both at the "traditional" behavior of every indicator as well as their deviations to this. Source


Chitu M.G.,Ovidius University | Zgan R.,Maritime University of Constanta
IOP Conference Series: Materials Science and Engineering | Year: 2015

Event of major accident navigation near offshore drilling rigs remains unacceptably high, known as the complications arising from the problematic of the general motions of the ship sailing under real sea. Dynamic positioning system is an effective instrument used on board of the ships operating in the extraction of oil and gas in the continental shelf of the seas and oceans, being essential that the personnel on board of the vessel can maintain position and operating point or imposed on a route with high precision. By the adoption of a strict safety in terms of handling and positioning of the vessel in the vicinity of the drilling platform, the risk of accidents can be reduced to a minimum. Possibilities in anticipation amplitudes of the oscillatory movements of the ships navigating in real sea, is a challenge for naval architects and OCTOPUS software is a tool used increasingly more in this respect, complementing navigational facilities offered by dynamic positioning systems. This paper presents a study on the amplitudes of the oscillations categories of supply vessels in severe hydro meteorological conditions of navigation. The study provides information on the RAO (Response Amplitude Operator) response operator of the ship, for the amplitude of the roll movements, in some incident wave systems, interpreted using the energy spectrum Jonswap and whose characteristics are known (significant height of the wave, wave period, pulsation of the wave). Ship responses are analyzed according to different positioning of the ship in relation to the wave front (incident angle ranging from 10 to 10 degree from 0 to 180), highlighting the value of the ship roll motion amplitude. For the study, was used, as a tool for modeling and simulation, the features offered by OCTOPUS software that allows the study of the computerized behavior of the ship on the waves, in the real conditions of navigation. Program library was used for both the vessel itself and navigation modeling environment, for regular waves as well for the irregular waves which was modeled using Jonswap energy spectrum.. Source


In this analysis, the variable configuration requires a variable distribution. This takes account of the areas offered by the valves and resistance gazodynamic coefficients. All at once the law of efficiency variation describes the variation of the power law. Cycle behavior was analyzed for the following values of the pressure drop coefficient on admission: 5%, 10%, 20% and 40%. For the calculations is necessary to determine the dimensionless heat developed by combustion. I used the following values: for the pressure drop coefficient on admission I use ψa=10 % and for the share of gazodynamic on the suction route conductance in total conductance I use Ka 0,5. With this configuration imposed and with Qcb 3,71 (dimensionless heat developed by combustion) resulted: pmi 10,255 (mean indicated pressure cycle); ηv = 0,876 (cylinder filling coefficient); α = 1,515 (excess air coefficient) and ηi = 0,499 (indicated cycle efficiency); Pi 1,851 (dimensionless indicated power); Qg 3,37 (dimensionless heat taken combustion gas);Q0 1534, (dimensionless heat taken environment). After numerical analysis result a maximum efficiency with relatively low dissipation. © (2014) Trans Tech Publications, Switzerland. Source


Omocea I.,Maritime University of Constanta
Advanced Materials Research | Year: 2014

We use a model that is based on the cycle behavior inlet pressure variation. This analysis revealed the two main regimes of operation marine propulsion engines. Pressure drop in the suction process can be seen from two points of view: this pressure drop is an active dissipation and at the same time is a passive dissipation, contributing to the deterioration of cycle infrastructure. Interference of the two effects is reflected by the appearance of a ψa opt=0,3...0,35, for which indicated power Pi becomes maximum in terms of given geometric and gazodynamic configurations. Respectively for a weighting of conductance gazodynamic Ka imposed. When fuel flow is imposed, the analysis revealed that the share of shall be amended to variation of ψa, which involves the geometric and gazodynamic configuration variable. In this numerical analysis showed the existence of ψa opt=0,1...0,15, for which indicated efficiency ηi is maximum. © (2014) Trans Tech Publications, Switzerland. Source

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