800 research outputs found
Networking innovation in the European car industry: does the open innovation model fit?
The demands of transportation have driven the automobile industry into an innovation race. Uncertain technological trends, long development cycles, highly capital-intensive product development, saturated markets, and environmental and safety regulations have subjected the sector to major transformations. The technological and organisational innovations related to these transformations necessitate research that can enhance our understanding of the characteristics of the new systems. The study investigates the applicability of the Open Innovation concept to a mature capital-intensive asset-based industry - the European automobile industry, which is preparing for a radical technological discontinuity. Purposely selected knowledgeable respondents were interviewed across seven European countries. The findings contribute to the understanding of the OI concept by identifying key obstacles to the wider adoption of the OI model in the European car industry, and signalling the importance of intermediaries and large incumbents for driving network development and OI practices as well as the need of new competencies to be developed by all players
Cosmic string Y-junctions: a comparison between field theoretic and Nambu-Goto dynamics
We explore the formation of cosmic string Y-junctions when strings of two
different types collide, which has recently become important since string
theory can yield cosmic strings of distinct types. Using a model containing two
types of local U(1) string and stable composites, we simulate the collision of
two straight strings and investigate whether the dynamics matches that
previously obtained using the Nambu-Goto action, which is not strictly valid
close to the junction. We find that the Nambu-Goto action performs only
moderately well at predicting when the collision results in the formation of a
pair of Y-junctions (with a composite string connecting them). However, we find
that when they do form, the late time dynamics matches those of the Nambu-Goto
approximation very closely. We also see little radiative emission from the
Y-junction system, which suggests that radiative decay due to bridge formation
does not appear to be a means via which a cosmological network of such string
would rapidly lose energy.Comment: 17 pages, 17 figures; typo correctio
Processing and properties of bone-analogue biodegradable and bioinert polymeric composites
This paper summarizes the processing and properties of bone-analogue composites aimed to be used in temporary or permanent
orthopaedic applications. The studied matrices were two biodegradable starch based blends (with ethylene-vinyl alcohol copolymer
or with cellulose acetate) and three high density polyethylene (HDPE) grades. Composites of these materials with hydroxyapatite
(HA—the main inorganic constituent of the human bone) were produced by extrusion compounding and subsequently injection
moulded. A non-conventional injection moulding technique known as shear controlled orientation in injection moulding
(SCORIM) was used deliberately to induce a strong anisotropic character to the processed composites. For the case of HDPE based
composites, an alternative reinforcement system based on carbon fibres (C fibres) was also studied. For that, a special moulding
technique that combines, in a single equipment, a compounding with an injection unit was used. Composites featuring a sandwich
like structure were also produced by mono-sandwich injection moulding. These composites combine a HDPE/HA outer layer and
HDPE/C fibre reinforced core. The aim is to produce composites with a mechanical behaviour matching that of human cortical
bone and simultaneously a strong bioactive (bone-bonding) character. For all the cases, the mechanical performance of the produced
composites was assessed and the structure developed investigated and related to the processing conditions. It was possible to
produce, both biodegradable and bioinert matrix composites, with properties that might allow for their application the orthopaedic orthopaedic field.Subprograma Ciência e Tecnologia do 2.º Quadro Comunitário de Apoio, Ministério da Ciência e Tecnologia (Portugal)
Structure development and control of injection-molded hydroxylapatite-reinforced starch/EVOH composites
This article reports on the development of novel composites of starch-based polymers reinforced with hydroxylapatite (HA). Two different grades of blends of starch and ethylene vinyl alcohol copolymers were reinforced with up to 30% (wt) of sintered and nonsintered HA. The initial compounding stage was carried out either in a rotating drum or by twin-screw extrusion (TSE). Compounds were injection molded using both conventional molding and a shear-controlled orientation in injection molding (Scorim) technique. It was possible to obtain composites with very good mechanical properties, approaching those of cortical bone. The best results were achieved for 30% sintered HA composites processed by TSE and Scorim, due to the in situ formation of HA fibers, and the development of molecular orientation and more compact microstructures in the moldings. This was confirmed by SEM analysis of the fracture surfaces, x-ray diffraction, and Raman spectroscopy. The biodegradability of the composites was also assessed and was found to be faster than that of the matrixPRAXIS XXI Programm
Reinforcement and structure development in injection molding of bone-analogue composites
Composites of high density polyethylene (HDPE) with hydroxyapatite (HA—the
main inorganic constituent of human bone) were produced by extrusion compounding
and subsequent injection molding. Shear controlled orientation in injection
molding (SCORIM) was used deliberately to induce a strong anisotropic character
in the composite materials. Bi-composite moldings featuring a sandwich like morphology
were also produced by mono-sandwich injection molding. These composites
combine a HDPE/HA outer layer and HDPE/carbon fiber reinforced core. For all the
cases, the mechanical performance of the produced composites was assessed and
the structure developed investigated and related to the processing conditions
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