Energy Efficiency Analysis of Trawlers (Case Study: Indonesian’s Trawler)

Nowadays, the energy efficiency is of most importance in all economical activities. For the fishing industry, it is particularly critical. Energy efficiency in the fishing sector can be expressed in term of the ratio of fishing capture over operational cost. The fuel cost in ship operation became a dominant factor of the total operational cost. Moreover, fuel cost is high and continues to increase. One way to achieve better energy efficiency is to use a high efficiency ship propeller in order to diminish fuel consumption.   Trawlers have two main operational conditions; they are the voyage condition and the trawling condition. The voyage condition is when the trawler travels to port and to the fishing grounds. The trawling condition is when the trawler pulls the trawl to catch fish. Most of trawler problem is in trawling operation with trawls, the ship resistance increased tremendously and then the propeller must work harder to ensure the ship can advance against the trawling resistance at low speed, 3, 5 Knots. This condition corresponds to a heavy load condition. In this condition, the propeller efficiency is low. Duct propeller is one of the configurations that increase the propeller efficiency in heavy loaded condition. The other strategy is to increase the energy efficiency is to optimize ship speed in voyage condition.  In this research, the numerical simulations performed for the propeller-duct interactions were made possible thank to an iterative procedure where the flow around each of the several components are modeled with a potential flow theory. Boundary element Method (BEM) or panel method is used to solve the potential flow model. The models and methods are described in the document as well as the iterative procedure that has been developed within the framework of this project. We have investigated energy efficiency with fuel consumption approach. Propeller with and without duct in same size (B3-65 and Kaplan 65 in Duct 19A) are analyzed and optimized ship speed 9 Knots to 7 Knots. It shows that 13.7 % of the fuel consumption was saved with a duct propeller in trawling condition and 35% of the fuel consumption was saved with an optimized ship speed in voyage condition

L'addiction à internet : une addiction au virtuel ?

International audienceL'apparition d'Internet dans le cercle des nouvelles technologies a permis d'ouvrir au monde entier des possibilités de communication et de rencontre. Le chat, l'e-mail, les jeux en réseau ou la recherche d'information ont trouvé leur place dans le quotidien de plus de 1,8 billion d'usagers dans le monde (Nua, 2005). Les internautes apprécient la facilité d'utilisation de ce média, son interactivité, son accessibilité, et le grand nombre d'informations diverses disponibles (Chou, 2001). D'ailleurs la plupart des adolescents interviewés (Chin-Chung & Sunny, 2003) reconnaissent que les messages sur Internet sont leur première source d'information et de savoir. 95 % d'entre eux utilisent cet outil dans le but de prendre duplaisir, de chercher des informations utiles, de « tuer le temps », de développer un sentiment d'appartenance, de contrôler l'environnement, et d'être familier avec d'autres usagers (Chou, 2001). Les possibilités de contrôle sur Internet sont attractives (Kandell, 1998) : l'internaute peut décider de discuter avec d'autres, ou d'arrêter la conversation quand il le souhaite, conserver son anonymat, tester de nouvelles identités, se dévoiler, ou se travestir

Évaluation du rôle des bio-additifs dans la dégradation des boues de fosse septique et conception de méthodes de mesure de l'activité méthanogène

Des additifs pour le traitement des fosses septiques sont proposés sur le marché, dans le but d’améliorer leur fonctionnement. Cependant, leur influence n’a pas été vérifiée. Un projet de recherche a été mis en place afin d’évaluer l’influence des bio-additifs sur la dégradation des boues de fosse septique. L’étude a été menée, à l’échelle du laboratoire, sur trois produits de traitement testés sur six échantillons différents d’effluents de fosses septiques vidangées. Un témoin (sans additif) a servi de référence pour évaluer la dégradation naturelle simulée des boues de fosse septique et la comparer à celle des bio-additifs. Ils ont été incubés à une température de 35°C, pendant une période de dix jours. Afin d’évaluer leur rôle dans le traitement, les paramètres suivants ont été mesurés : solides totaux, solides volatils, demande chimique en oxygène, coliformes fécaux et production de méthane. Ces paramètres ont été mesurés avant le lancement, à la moitié (5 jours) et à la fin de chaque essai. Les analyses statistiques des résultats obtenus (analyse de la variance et test de Dunnett) n’ont pas permis de mettre en lumière une différence significative entre les bio-additifs utilisés et le témoin, à un seuil de confiance de α=0,05. Une partie du projet s’est également concentrée sur la conception de méthodes de mesure du méthane en laboratoire. Les expériences ont été menées en parallèle avec celles menées sur les bio-additifs. Les résultats de l’étude statistique semblent être concluants concernant la fiabilité des mesures faites avec les montages expérimentaux conçus en laboratoire.Additives for septic tank treatment are available in order to improve their performance. However, their influence has not yet been proven. A research project was initiated to assess the influence of bio-additives on septic tank sludge degradation. The study was conducted at laboratory scale with regard to three treatment products tested on six different effluent samples from emptied septic tanks. A blank (without additive) was used as a reference to assess the natural degradation of septic tank sludge and to compare with the effects of the bio-additives. These samples were incubated at 35°C for ten days. In order to evaluate the bio-additive contribution, the following parameters were measured: total solids, volatile solids, chemical oxygen demand, fecal coliforms and methane production, and that before, halfway and at the end of each test. The statistical analysis of the results (analysis of variance and Dunnett’s test) was inconclusive to highlight a difference between the bio-additives and the reference at a confidence level of 5%. Another part of this project was to design laboratory methods for methane measurement. These tests were conducted at the same time as the bio-additives experiments. The statistical results seem conclusive as to the reliability of the measurements made with the experimental apparatus designed in the laboratory

Application of 2nd Generation Intact Stability Criteria on Naval Ships

The second generation intact stability criteria are currently under finalization and validation at the IMO. These criteria are organized in five stability failure modes and three levels of vulnerability assessment in each failure mode. Although this new regulation will not apply to naval ships, it is interesting to investigate the behavior of this vessel typology as well, due to their geometry and typical Froude number. This paper deals with of the pure loss of stability and parametric roll phenomena. Level one and level two vulnerability criteria for three naval ships of different size (helicopter carrier, destroyer, offshore patrol vessel) are applied. Results show an overall satisfactory behavior of the three ships investigated by the new regulation, for both failure stability modes

Cerebellar cortex granular layer interneurons in the macaque monkey are functionally driven by mossy fiber pathways through net excitation or inhibition

The granular layer is the input layer of the cerebellar cortex. It receives information through mossy fibers, which contact local granular layer interneurons (GLIs) and granular layer output neurons (granule cells). GLIs provide one of the first signal processing stages in the cerebellar cortex by exciting or inhibiting granule cells. Despite the importance of this early processing stage for later cerebellar computations, the responses of GLIs and the functional connections of mossy fibers with GLIs in awake animals are poorly understood. Here, we recorded GLIs and mossy fibers in the macaque ventral-paraflocculus (VPFL) during oculomotor tasks, providing the first full inventory of GLI responses in the VPFL of awake primates. We found that while mossy fiber responses are characterized by a linear monotonic relationship between firing rate and eye position, GLIs show complex response profiles characterized by "eye position fields" and single or double directional tunings. For the majority of GLIs, prominent features of their responses can be explained by assuming that a single GLI receives inputs from mossy fibers with similar or opposite directional preferences, and that these mossy fiber inputs influence GLI discharge through net excitatory or inhibitory pathways. Importantly, GLIs receiving mossy fiber inputs through these putative excitatory and inhibitory pathways show different firing properties, suggesting that they indeed correspond to two distinct classes of interneurons. We propose a new interpretation of the information flow through the cerebellar cortex granular layer, in which mossy fiber input patterns drive the responses of GLIs not only through excitatory but also through net inhibitory pathways, and that excited and inhibited GLIs can be identified based on their responses and their intrinsic properties

Design of composite ducted horizontal axis tidal turbine

The marine current turbine is the mechanical device that captures the kinetic energy of marine current to generate electrical power. A panel method program coupled with the blade element momentum theory (BEM) was used to design a bare tidal turbine which reaches 88% of the Betz limit. The addition of a duct for a same overall cross section area has been investigated. The numerical results show that the ducted turbine’s power coefficient, which was computed using the overall cross section area, can be slightly increased if a camber duct profile with a flare angle is used. The hydrodynamic pressure obtained with the panel method code were then implemented as boundary conditions to a finite element analysis (FEA) in order to compute the mechanical behavior, stress distribution and deflection of the duct in composite material. The Hashin criterion was used for damage prediction

Acoustical measurement of the shear modulus for thin porous layers

International audienceSimulations performed with the Biot theory show that for thin porous layers, a shear mode of the structure can be induced by a point-source in air located close to the layer. The simulations show that this mode is present around frequencies where the quarter wavelength of the shear Biot wave is equal to the thickness of the samples and show that it can be acoustically detected from the fast variations with frequency of the location of a pole of the reflection coefficient close to grazing incidence. The mode has been detected with this method for two reticulated plastic foams. For one of the foams studied, the velocity and the damping of the Rayleigh wave have been measured on a thicker layer of the same medium at higher frequencies, giving a real part of the shear modulus close to the one obtained from the measured location of the pole. The strong coupling of the shear mode with the acoustic field in air allows the measurement of the shear modulus without mechanical excitation