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This work reports on a study concerning the behaviour of an elastic system subject to a periodic external excitation. Oscillatory movement is the most common type of mechanical movement found in nature and, of course, in technique. A system executing simple harmonic motion is called harmonic oscillator system. If the harmonic oscillator motion describes a path as the straight line, the harmonic oscillator is called linear harmonic oscillator. Such linear harmonic oscillator is considered an elastic system when the force acts upon it is an elastic one. If in the elastic system dissipative forces are involved then they have the effect of energy losses during oscillation, so that, after a while, the oscillator energy is lost in various forms. To compensate the energy losses of dissipative forces, the oscillator must be driven by a periodic external disturbing force that produces forced oscillations in the elastic systems. If external disturbing force is periodical, the oscillator will run a new type of oscillations called forced oscillations. In this case the period and frequency of forced oscillations of the elastic system will be the same as the period and frequency of disturbing force. In this situation there is a transfer of energy between the two systems. Studying forced vibrations, in terms of energy intake, through excitation forces, are overrun highlight the importance of phase shift between force and oscillator movement. Keywords: harmonic oscillator system, periodic external excitation, phase shift, energy, resonance phenomenon

This paper presents a procedure for the calculus and dimensional optimization using finite elements analysis of a polymeric retractable rod which replaces a metallic one. This rod is an element of the front auger embedded in a technological equipment. The mechanism is 3D modeled in SolidWorks. CosmosMotion is then used to simulate and analyze the motion of the mechanism and to calculate the loads acting on the rod during its movement. These loads are then exported in CosmosWorks – a finite elements analysis software – which is used here to perform stress analysis and to optimize the retractable rod’s dimensions. Keywords: polymers, optimization, finite elements analysis

The chitosan based nanofibers web is a biocompatible, biodegradable, antimicrobial and non-toxic structure which has both physical and chemical properties to effectively capture and neutralize toxic pollutants from air and liquid media. Despite such potentials, the mechanical properties of nanofibers web is very poor to use in filtration applications. To remedy this defect, nanofibers web could laminate into a strength structure. The purpose of this study is to consider the influence of laminating temperature on nanofibers web/multilayer structure properties. The nanofibers web morphology and multilayer cross-section was observed under an optical microscope and scanning electron microscope, respectively. Also, air permeability experiments were performed to examine the effect of laminating temperature on air transport properties of multilayer structures. Optical microscope images showed that the nanofiber web began to damage when laminating temperature was selected above melting point of adhesive layer. Air permeability decreased with increasing laminating temperature. It is also observed that the adhesive force between layers was increased by increasing laminating temperature. Keywords: chitosan, nanofibers web, filtration, lamination

Polymer materials for denture bases, with thermal or light polymerization are relatively fragile, being considered brittle materials from the Fracture Mechanics concepts point of view. This paper presents a comparative study on determination of fracture toughness for 2 types of resins used in complete dentures technology: heat-curing resin (Meliodent), and light-curing resin (Eclipse). The tests were performed on a static loading machine, model Zwick/Roell of 5kN. The results obtained by 2 methods differ no more than 10-15%. Both methods showed that Eclipse has a better resistance to fracture than Meliodent. Keywords: acrylic resins, complete dentures, fracture toughness

The paper presents a study on the waste polypropylene modification with styrene-isoprene block-copolymers in correlation with elastomers molecular weight. The modification of this polyolefin improves the mechanical properties, especially the impact strength. Keywords: styrene-isoprene block-copolymers, waste polypropylene, melt blending

Solid waste disposal is a significant to overhead in a shipyard environment. In many areas of Galati the disposal capacity is being reduced and the cost of disposal is continuing to climb. The study of the behaviour of bitumen mixtures is an old subject in the literature. Many specialists have been trying to replace the sand with recycled materials resulting from blasting ship parts. The main purpose of this study is obtaining a bitumen mixture with a good behaviour to long use. The grit is an abrasive blasting material (ABM), having an angular form, used in ship repair processes prior to the application of coatings. It is produced by the pulverization of molten steel, followed by a series of thermal and mechanical treatments in order to give the product its final characteristics. The shipyard in Galati generates annually thousands of tons of used blast grit and they dispose of it in landfills or directly into the Danube as a usual practice. We intend to find possibilities of disposing the wastes produced by shipyards, our research being focused on achieving the sustainable development requirements of the civil society. Environmentally speaking, recycling spent ABM has the potential to significantly reduce waste generation while saving money. Keywords: mix asphalt, grit, recycling, shipyard

In the present study we evaluated the applicability of laser Doppler line scanning in recording the gingival healing process after a surgical procedure followed by two types of plastic provisional restoration. The laser Doppler imaging is a non-invasive method for analyzing the perfusion map of a certain area and can be used in order to establish the health status of a certain region after surgical treatment. The two types of plastic temporaries had no negative influence on the healing process. Key words: composite materials, laser Doppler imaging, microcirculation, non-invasive diagnosis, real time imaging

A biopsy sample that was taken from neurosurgery then introduced into the solution of formaldehyde was examined with Time Domain optical coherence tomography. The results are inconclusive and so that preserving was accomplished by plastination the tissue sample in which the degree of rigidity of the sample is controlled without destroying the tissue. Keywords: Plastination, Optical Coherence Tomography, nervous system

The present study pursues the influence of polyelectrolytes based on maleic co-polymers with styrene (NaM-S) and vinyl acetate (NaM-VA) under the form of natrium salt, on the colour parameters CIE L*, a*, b* of the Melana-type polyacrylonitrile fibres dyed with Crystal Violet. The colour differences are ascribed to the modifications appeared in the colour components, in terms of concentration, polyelectrolyte character and tinctorial parameters: dyeing duration and temperature. Keywords: maleic anionic polyelectrolytes, Crystal Violet, Melana - type polyacrylonitrile fibres, colour parameters CIE L*a*b*

The kinetic approach on thermal stabilization of LDPE in the presence of 7 chalcone compounds is presented. The application of zero order or first order treatment to the experimental date obtained for stabilized LDPE has revealed that the depletion of antioxidant is a first order process. The comparison of the most efficient member of chalcone series and some commercial phenolic antioxidants has provided the following sequence for the prevention of oxidation: ETANOX – 330 ] D4 ] IRGANOX – 1076 ] CYANOX – 2246 ] TOPANOL – OC ]] purified LDPE