1,720,994 research outputs found
Level 1 vulnerability criterion for the dead ship condition: A practical methodology for embedding operational limitations
Full text linkThe framework of second generation intact stability criteria (MSC.1/Circ.1627) allows introducing so-called “operational limitations”, by specifying alternative environmental conditions based on the expected operation of the ship. Relevant calculation parameters of the criteria are correspondingly modified, according to standardized procedures specified by the Explanatory Notes. This is a significant novelty, and information is available for implementing operational limitations for most of the failure modes and levels of assessment. However, this is not the case for the level 1 vulnerability criterion for the dead ship condition. Therefore, the paper investigates the development of a rational simple procedure to contribute filling this gap. The devised approach provides a tool for determining a modified reference wind speed based on the environmental conditions representative of the considered operational limitations. Specifically, the modified wind speed is defined as the wind speed with a specified probability of exceedance. The reference probability of exceedance is determined considering the standard conditions and assumptions in the framework of MSC.1/Circ.1627. The modified reference wind speed can then be used to re-define all the calculation parameters of the criterion, according to the relevant theoretical background. Two example applications of the devised approach are also provided
LA PARTECIPAZIONE DELLA COMUNITA' LOCALE ALLA COSTRUZIONE DELLE POLITICHE SOCIALI
No full textIl capitolo propone una riflessione sul contributo che la comunità locale può dare alla costruzione di politiche sociali orientate alla costruzione di benessere a partire dalla presentazione di alcuni dei risultati emersi dalla ricerca "Regionalizzazione del servizio sociale e trifocalità del servizio sociale" condotta nell'ambito del del progetto PRIN "Servizio sociale e territorio. I cambiamenti del servizio sociale nei processi di regionalizzazione delle politiche sociali"
On the Roll Motion of a Ship with Partially Filled Unbaffled and Baffled Tanks: Part 1: Mathematical Model and Experimental Setup – Part 2: Numerical and Experimental Analysis
No full textTheoretical, numerical and experimental study on the problem of ergodicity and 'practical ergodicity' with an application to parametric roll in longitudinal long crested irregular sea
No full textThis paper addresses the problem of ergodicity of stochastic processes starting from a theoretical point of view, with the aim of obtaining a deeper understanding for practical applications. The problem is tackled bearing in mind the concept of 'practical ergodicity', that is, the possibility of obtaining reliable information about ensemble averages by using temporal averages. Some general analytical tools are given to address the problem of accuracy of temporal averages and an example of their use in a possible design of experiments is given. A series of Monte Carlo numerical simulations are performed by means of an analytical non-linear 1.5-DOF model of parametrically excited roll motion. The outcomes of such simulations are analysed to show the effect of ship speed and sea spectrum shape. The effect of wave grouping phenomenon is discussed with particular attention to the Doppler effect. Qualitative indications given by the numerical simulations are then compared with experimental tests showing a good agreement. Practical ergodicity of generated sea in towing tank is also briefly addressed. (C) 2005 Elsevier Ltd. All rights reserved
Nonlinear and stochastic aspects of parametric rolling modeling
No full textThis paper addresses, starting from an extensive series of tests in longitudinal regular waves (already done) and irregular waves (in progress), the problems connected with the threshold formulation for parametric rolling and its amplitude modeling above threshold. Both head and following waves have been considered, also in view of the greater attention to head sea conditions called for during International Maritime Organisation Subcommittee on Stability and Load Lines, and on Fishing Vessels Safety (IMO/ SLF) discussion on the revision of the Intact Stability Code. Particular attention is given in the regular wave case to the nonlinear damping, nonlinear restoring, and nonlinear parametric excitation terms. The mathematical models so developed are "compared" with experimental results by means of an ad hoc parameter estimation technique. It is, on the other hand, well known that several different thresholds can be proposed in the case of irregular waves and that the nonlinear modeling of roll motion variance above threshold is at present not properly addressed. Here, too, a series of experiments will be conducted in the presence of narrow band irregular waves having the bandwidth as parameter. A mathematical description of the nonlinear parametric rolling can be obtained with the use of approximate analytical techniques
On the roll motion of a ship with partially unbaffled and baffled tanks. Part I: mathematical model and experimental setup
No full textOn the nonlinear modeling of parametric rolling in regular and irregular waves
No full textThis paper summarizes the results and the problems still open regarding the development of a 1.5DOF nonlinear mathematical model of the parametric rolling in longitudinal waves with particular regard to the head sea condition. A first part is devoted to the case of regular waves, while the second concerns parametric rolling generated by irregular waves obtained by means of white noise filtered through a linear filter with adjustable bandwidth and by using a Bretschneider spectrum. The availability of an extensive series of test results on scale models conducted at University of Trieste and at INSEAN, allows a thorough discussion of the problems connected with the threshold formulation for parametric rolling and its amplitude modelling above threshold
On the roll motion of a ship with partially unbaffled and baffled tanks. Part II: numerical and experimental analysis
No full textA contribution on the problem of practical ergodicity of parametric roll in longitudinal long crested irregular sea
No full text- …
