System-based maneuvering simulation of a ship navigating in the confined waterway

The system-based maneuvering simulations were conducted to investigate the ship navigating in the confined waterway. The confinement effect was included using the model of Vantorre [1]. The maneuvering model was validated using the turning circle and zigzag tests, and the confinement model was verified using the experimental data of Norrbin [2]. The good agreement proved the validity of our method. Using this method, the influences of the ship-bank distance and the propeller rate of turn were studied and concluded. Small ship-bank distance and large propulsion were proved to enhance the confinement effect

Influence of the draft to ship dynamics in the virtual tank based on openFOAM

A virtual tank is built based on OpenFOAM. The mesh is created using the ’blockMesh’ and the ’snappyHexMesh’ utilities successively. The ’interDyMfoam’ solver is used to solve the flow fields. The results are compared with the experimental data of the Tokyo 2005 CFD workshop, which show good agreement. The cases with seven different drafts are further simulated. It is found that a small draft can make the ship unstable and weaken the effect of the bulbous bow

Numerical prediction of ship resistance and squat in confined waters

Accurate prediction of hydrodynamic forces opposing a ship displacement in restricted waterways is necessary in order to improve energy efficiency of inland transport. When a ship moves in restricted waterways, a significant increase in ship squat (combination of sinkage and trim) and resistance occurs compared to a movement in open waters. In this paper, a 3D numerical model based on fluid-structure coupling is presented and used to investigate the effect of limited water depth and channel width on ship resistance and squat

Dynamic estimation of bank-propeller interaction effect on ship maneuvering using CFD method coupled to 6DOF algorithm

This paper presents a numerical investigation of ship maneuvering under the combined effect of the bank and propeller. The incompressible turbulent flow with free surface around the self-propelled hull form is simulated using a commercial CFD software (Fluent). In order to estimate the dynamic effect of bank and propeller, the CFD model with the dynamic mesh setting is coupled to the 6DOF module to compute the ship motion due to hydrodynamic forces. The numerical simulations are carried using the equivalent experiment conditions. The validation of the CFD model is performed by comparing the numerical results to the experimental data

Bias-Dependent Generation and Quenching of Defects in Pentacene

We describe a defect in pentacene single crystals that is created by bias stress and persists at room temperature for an hour in the dark but only seconds with 420nm illumination. The defect gives rise to a hole trap at Ev + 0.38eV and causes metastable transport effects at room temperature. Creation and decay rates of the hole trap have a 0.67eV activation energy with a small (108 s-1) prefactor, suggesting that atomic motion plays a key role in the generation and quenching process.Comment: 10 pages, 3 figure

Gène Cou Nu (Na) et activité en open field chez le jeune Poussin

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Quantum theory of dissipation of a harmonic oscillator coupled to a nonequilibrium bath; Wigner-Weisskopf decay and physical spectra

We extend the quantum theory of dissipation in the context of system-reservoir model, where the reservoir in question is kept in a nonequilibrium condition. Based on a systematic separation of time scales involved in the dynamics, appropriate generalizations of the fluctuation-dissipation and Einstein's relations have been pointed out. We show that the Wigner-Weisskopf decay of the system mode results in a rate constant which depending on the relaxation of nonequilibrium bath is dynamically modified. We also calculate the time-dependent spectra of a cavity mode with a suitable gain when the cavity is kept in contact with a nonequilibrium bath.Comment: Plain Latex, 28 pages, 2 PS figure

Worldwide food recall patterns over an eleven month period: A country perspective.

<p>Abstract</p> <p>Background</p> <p>Following the World Health Organization Forum in November 2007, the Beijing Declaration recognized the importance of food safety along with the rights of all individuals to a safe and adequate diet. The aim of this study is to retrospectively analyze the patterns in food alert and recall by countries to identify the principal hazard generators and gatekeepers of food safety in the eleven months leading up to the Declaration.</p> <p>Methods</p> <p>The food recall data set was collected by the Laboratory of the Government Chemist (LGC, UK) over the period from January to November 2007. Statistics were computed with the focus reporting patterns by the 117 countries. The complexity of the recorded interrelations was depicted as a network constructed from structural properties contained in the data. The analysed network properties included degrees, weighted degrees, modularity and <it>k</it>-core decomposition. Network analyses of the reports, based on 'country making report' (<it>detector</it>) and 'country reported on' (<it>transgressor</it>), revealed that the network is organized around a dominant core.</p> <p>Results</p> <p>Ten countries were reported for sixty per cent of all faulty products marketed, with the top 5 countries having received between 100 to 281 reports. Further analysis of the dominant core revealed that out of the top five transgressors three made no reports (in the order China > Turkey > Iran). The top ten detectors account for three quarters of reports with three > 300 (Italy: 406, Germany: 340, United Kingdom: 322).</p> <p>Conclusion</p> <p>Of the 117 countries studied, the vast majority of food reports are made by 10 countries, with EU countries predominating. The majority of the faulty foodstuffs originate in ten countries with four major producers making no reports. This pattern is very distant from that proposed by the Beijing Declaration which urges all countries to take responsibility for the provision of safe and adequate diets for their nationals.</p

Sensitivity analysis of erosion on the landward slope of an earthen flood defense located in southern France submitted to wave overtopping

The study aims to provide a complete analysis framework applied to an earthen dike located in Camargue, France. This dike is regularly submitted to erosion on the landward slope that needs to be repaired. Improving the resilience of the dike calls for a reliable model of damage frequency. The developed system is a combination of copula theory, empirical wave propagation, and overtopping equations as well as a global sensitivity analysis in order to provide the return period of erosion damage on a set dike while also providing recommendations in order for the dike to be reinforced as well as the model to be self-improved. The global sensitivity analysis requires one to calculate a high number of return periods over random observations of the tested parameters. This gives a distribution of the return periods, providing a more general approach to the behavior of the dike. The results show a return period peak around the 2-year mark, close to reported observation. With the distribution being skewed, the mean value is higher and is thus less reliable as a measure of dike safety. The results of the global sensitivity analysis show that no particular category of dike features contributes significantly more to the uncertainty of the system. The highest contributing factors are the dike height, the critical velocity, and the coefficient of seaward slope roughness. These results underline the importance of good dike characterization in order to improve the predictability of return period estimations. The obtained return periods have been confirmed by current in situ observations, but the uncertainty increases for the most severe events due to the lack of long-term data.</p

Influence du gène Na (« Cou-nu ») sur la croissance, la consommation alimentaire et la composition corporelle du poulet selon la température ambiante

International audienc