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Issue 11, Volume 2, November 2007
Print ISSN: 1991-8747
E-ISSN: 2224-3429







Title of the Paper: Complex study on hand-arm system exposed to vibrations


Authors: Simona Lache

Abstract: The research performed in the domain of human body vibrations revealed their important influence on human health, being the origin of several professional diseases. Consequently, the vibrations influence can be clearly systematized in two distinct categories: whole body vibrations with significant effects in the entire human body; vibrations on different sections of the body that transmit significant accelerations and displacements only in some sections, such as the hand-arm system. While the first category registered mainly in the professional driving sector has been constantly studied and different solutions for vibration attenuation have been proposed, the hand-arm vibration domain is still open for discussions. This paper presents a complex study both from the medical and engineering point of view regarding the modelling and testing methods used for hand-arm system vibrations in the view of professional diseases prevention. It aims to evaluating preventive strategies to reduce worker exposures to hand-arm transmitted vibration and to decrease the occurrence of Hand-Arm Vibration Syndrome (HAVS) in workers.

Keywords: hand-arm vibrations, occupational health, daily exposure assessment, modelling and simulation.

Title of the Paper: A new study on the optimal prediction of partial transmission ratios of three-step helical gearboxes with second-step double gear-sets


Authors: Vu Ngoc Pi

Abstract: This paper presents a new study on the applications of the optimization and regression techniques for optimal prediction of partial ratios of three-step helical gearboxes with second-step double gear-sets for getting different objectives including the minimal gearbox length, the minimal gearbox cross section dimension and the minimal mass of gears. In the study, based on the condition of the moment equilibrium of a mechanic system including three gear units and their regular resistance condition, three optimization problems for getting minimal gearbox length, the minimal gearbox cross section dimension and minimal mass of gears were performed. In addition, explicit models for calculating the partial ratios of the gearboxes were found by using regression analysis technique. Using these models, the determination of the partial ratios becomes accurate and simple.

Keywords: Gearbox design; Optimal design; Helical gearbox; Transmission ratio.

Title of the Paper: Permeability Effect on the capillary and the viscous forces during the drainage process in porous media


Authors: Chakib Seladji

Abstract: Two-phase flow and capillarity phenomenon in porous solids are well known in physics and engineering. In different studies, drainage experiments in porous media, initially saturated with a wetting fluid, have been largely devoted by using various type of fluids and different angle values of slant to the horizontal direction, in order to evaluate the effects of gravity forces and the injection flow-rate. However, the influence of the matrix structure on the capillary and viscous forces as well as the fluids distribution has not been treated sufficiently. In this study, we simulate an ascending air phase flow in a vertical porous channel initially saturated with a liquid phase, in order to evaluate the two previous effects. The numerical study is performed for large range of injected air mass flow rate along the porous channel from the bottom up. The different forces intervening in the drainage process is analyzed according to several permeabilities. The results show that for a weak gas mass flow rate, the capillary effect is dominant and the gas saturation in a porous channel is proportional to the permeability. For more important gas mass flow rate, the saturation behavior becomes inversely proportional to the permeability of the porous channel.

Keywords: two-phase flow, capillary pressure, viscosity forces, relative permeability, saturation behavior

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