830 research outputs found
Geotraceability and life cycle assessment in environmental life cycle management: towards sustainability.
Sustainability is an emerging concept in product chains and integrates environmental, social, and economic aspects during the product's life cycle. Recently, the demand for environmental quality has required information about the products' life cycle. Life Cycle Assessment (LCA) includes the inventory analysis, where the productsÂŽlife cycle are systematized, and the Life Cycle Impact Assessment, when the environmental impacts potentials are calculated. A powerful tool to describe the history, use, and lication of a product in called geotraceability..
Internal structure of nanoparticles of Al generated by laser ablation in liquid ethanol
Al NPs are synthesized by laser ablation of a bulk Al target immersed into
liquid ethanol saturated with hydrogen at atmospheric pressure. The
nanoparticles possess a well-distinguished core-shell structure. High
Resolution Transmission Electron Microscopy shows several layers inside the Al
nanoparticle: oxide layer, amorphous Al, single crystal Al, and a cavity in the
center. Formation of the cavity is attributed to the sharp increase of hydrogen
dissolution in Al upon its melting and its eventual release after the
solidification
La perspectiva filosĂłfica de un concepto: una analogĂa de Bachelard
Es nuestra intenciĂłn en este trabajo, construir las imĂĄgenes analĂłgicas que implĂcitamente
estĂĄn bocetadas en "La filosofĂa del no" de Bachelard, tratando de mostrar a un Bachelard
analĂłgico al momento de exponer sus ideas, mostrĂĄndonos como la ciencia misma ha recurrido a
imĂĄgenes que al destruirlas condujeron al pensamiento cientĂfico a descubrir sus leyes orgĂĄnicas.
AsĂ vemos como Bachelard si bien marca una ruptura entre las imĂĄgenes, metĂĄforas y analogĂas
de la experiencia cotidiana, nos muestra la necesidad de recurrir a ellas por parte de la ciencia, la
cuål crea formas realistas y racionales de sus objetos que le otorgan una razón polémica. La
historia de la imaginerĂa cientĂfica conforma un plan estratĂ©gico pedagĂłgico ineluctable para el
crecimiento cientĂfico (Bachelard, 2003:115)
An implicit method for radiative transfer with the diffusion approximation in SPH
An implicit method for radiative transfer in SPH is described. The diffusion
approximation is used, and the hydrodynamic calculations are performed by a
fully three--dimensional SPH code. Instead of the energy equation of state for
an ideal gas, various energy states and the dissociation of hydrogen molecules
are considered in the energy calculation for a more realistic temperature and
pressure determination. In order to test the implicit code, we have performed
non--isothermal collapse simulations of a centrally condensed cloud, and have
compared our results with those of finite difference calculations performed by
MB93. The results produced by the two completely different numerical methods
agree well with each other.Comment: 25 pages, 9 figure
Impact behavior of injected PP/nanoclay parts
This work attempts to contribute to bridge the gap between scientific challenges and industrial stakes regarding
PP/nanoclay composites. Pieces of nanocomposites were obtained by direct injection of commercial PP mixed with a
commercial MB of PP with 50% of organoclay, with a double-gated hot runner mould, which produced mouldings with
a weld line. The moulding microstructure was assessed by POM and XRD, while the distribution and exfoliation grade
of clay was evaluated by TEM and XRD. The typical skin-core structure was found, with a skin thickness wider in bulk
than in weld line zones. Regarding clay platelets mostly intercalated structures were seen. The impact properties at
room temperature were assessed by means of tensile and biaxial tests. Properties were monitored at different sites of the
mouldings. At the weld line zone less energy was consumed under tensile conditions and exhibited higher apparent
impact toughness under biaxial conditions than the bulk zone. Visual inspection of biaxially impacted samples showed
that the orientation of polymer molecules and clay platelets induced by melt flow prevailed, and the weld line was not
the determinant of the toughness of the mouldings. An optimum in impact performance was found for moulding with
3% of clay, since at larger clay contents platelets agglomerated and acted as stress raisers
Uni- and biaxial impact behavior of double-gated nanoclay-reinforced polypropylene injection moldings
Polypopylene/nanoclay three-dimensional parts were
produced without intermediate steps by direct injection
molding to explore the influence of flow features and
nanoclay incorporation in their impact performance.
The nanocomposite was obtained by direct compounding
of commercial PP with nanoclay masterbatch. The
as-molded morphology was analyzed by X-ray and
TEM analyses in terms of skin-core structure and
nanoclay particle dispersion. The nanoclay particles
induced the reduction of b-form spherulites, a known
toughener. The impact behavior was assessed in tensile
and biaxial modes. The PP nanocomposite molding
toughness was practically unaffected by the processing
melt temperature and flow rate. Conversely the
nanoclay presence is influent in the impact performance.
Under biaxial stress impact, the regions close to
weld lines are tougher than the bulk and the fracture
develops with main crack paths along the flow direction
and the weld line. Cracking along the weld line
results from less macromolecular interpenetration and
chain entanglement, and unfavorable nanoparticle orientation.
It seems that a failure mechanism which
involves nanoclay delamination and multiple matrix
crazing explains the toughening of PP in the directions
where the nanoparticle orientation with respect to
loading is adequate.Contract grant sponsors: CONICET, ANPCyT from Argentina, MINCyT (Argentina) - FCT (Portugal), Universities Nacional de Mar del Plata and Minho
Tuning complex shapes in Pt(0) nanoparticles : from cubic dendrites to five-fold stars
A platinum star performance: Quasi-single-crystalline Pt nanoparticles with peculiar morphologiesâcubic dendrites, planar tripods, and fivefold starsâwere synthesized in high yield. Shape selectivity was achieved by finely tuning the growth kinetics under a dihydrogen atmosphere
Stat3 controls tubolointerstitial communication during CKD
Functional Genomics of Systemic Disorder
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