Transient periodic behaviour related to a saddle-node bifurcation

The authors investigate transient periodic orbits of dissipative invertible maps of R2. Such orbits exist just before, in parameter space, a saddle-node pair is formed. They obtain numerically and analytically simple scaling laws for the duration of the transient, and for the region of initial conditions which evolve into transient periodic orbits. An estimate of this region is then obtained by the construction-after extension of the map to C2-of the stable manifolds of the two complex saddles in C2 that bifurcate ino the real saddle-node pai

Bounds for bounded motion around a perturbed fixed point

We consider a dissipative map of the plane with a bounded perturbation term. This perturbation represents e.g. an extra time dependent term, a coupling to another system or noise. The unperturbed map has a spiral attracting fixed point. We derive an analytical/numerical method to determine the effect of the additional term on the phase portrait of the original map, as a function of the δ bound on the perturbation. This method yields a value δ c such that for δδ c the orbits about the attractor are certainly bounded. In that case we obtain a largest region in which all orbits remain bounded and a smallest region in which these bounded orbits are captured after some time (the analogue of 'basin' and 'attractor respectively')

Understanding the build-up of a Technological Innovation System around Hydrogen and Fuel Cell Technologies

This study provides insight into the development of hydrogen and fuel cell technologies in the Netherlands (1980-2007). This is done by applying a Technological Innovation System (TIS) approach. This approach takes the perspective that a technology is shaped by a surrounding network of actors, institutions and technologies. When a technology is in an early stage of development, a TIS has yet to be built up in order to propel technological progress. This paper focuses on the historical build-up of the hydrogen and fuel cell innovation system in the Netherlands. The research focuses on processes that accelerated or slowed down the developments of hydrogen and fuel cell technologies. We suggest that this framework is helpful for actors who intend to accelerate the development and deployment of hydrogen and fuel cells in other countries.fuel cell; technological innovation system; system functions; cumulative causation.

Contemporary Innovation Policy and Instruments: Challenges and Implications

In this paper we review major theoretical (neoclassical economics, evolutionary, systemic and knowledge-based) insights about innovation and we analyse their implications for the characteristics of contemporary innovation policy and instruments. We show that the perspectives complement each other but altogether reveal the need to redefine the current general philosophy as well as the modes of operationalisation of contemporary innovation policy. We argue that systemic instruments ensuring proper organisation of innovation systems give a promise of increased rates and desired (more sustainable) direction of innovation.systemic instruments, innovation policy, innovation theory, policy mix, innovation system, sustainability

Understanding the formative stage of Technological Innovation System development. The case of natural gas as an automotive fuel

This study contributes to insights into mechanisms that influence the successes and failures of emerging energy technologies. It is assumed that for an emerging technology to fruitfully develop, it should be fostered by a Technological Innovation System (TIS), which is the network of actors, institutions and technologies in which it is embedded. For an emerging technology a TIS has yet to be built up. The research focuses on the dynamics of this build-up process by mapping the development of seven key activities: so-called system functions. The main contribution revolves around the notion of cumulative causation, or the phenomenon that the build-up of a TIS may accelerate due to system functions reinforcing each other over time. As an empirical basis, an analysis is provided of the historical development of the TIS around automotive natural gas technology in the Netherlands (1970-2007). The results show that this TIS undergoes a gradual build-up in the 1970s, followed by a breakdown in the 1980s and, again, a build-up from 2000-2007. It is shown that, underlying these trends, there are different forms of cumulative causation, here called motors of innovation. The study provides strategic insights for practitioners that aspire to support such motors of innovation.functions of technological innovation systems; cumulative causation; automotive natural gas.

Molecule sublimation as a tracer of protostellar accretion: Evidence for accretion bursts from high angular resolution C18O images

The accretion histories of embedded protostars are an integral part of descriptions of their physical and chemical evolution. In particular, are the accretion rates smoothly declining from the earlier toward later stages or in fact characterized by variations such as intermittent bursts? We aim to characterize the impact of possible accretion variations in a sample of embedded protostars by measuring the size of the inner regions of their envelopes where CO is sublimated and relate those to their temperature profiles dictated by their current luminosities. Using observations from the Submillimeter Array we measure the extents of the emission from the C18O isotopologue toward 16 deeply embedded protostars. We compare these measurements to the predicted extent of the emission given the current luminosities of the sources through dust and line radiative transfer calculations. Eight out of sixteen sources show more extended C18O emission than predicted by the models. The modeling shows that the likely culprit for these signatures is sublimation due to increases in luminosities of the sources by about a factor five or more during the recent 10,000 years - the time it takes for CO to freeze-out again on dust grains. For four of those sources the increase would have had to have been a factor 10 or more. The compact emission seen toward the other half of the sample suggests that C18O only sublimates when the temperature exceeds 30 K - as one would expect if CO is mixed with H2O in the grain ice-mantles. The small-number statistics from this survey suggest that protostars undergo significant bursts about once every 20,000 years. This also illustrates the importance of taking the physical evolutionary histories into account for descriptions of the chemical structures of embedded protostars.Comment: Accepted by A&A; 11 pages, 5 figure

Premium differentiation in social insurance

Premium differentiation in disability insurance encourages employers to improve working conditions in order to combat disability. Furthermore, by introducing competition in disability insurance, the implementation and administration of the insurance becomes more efficient. This advantage does not apply to premium differentiation in unemployment schemes because the unemployment risk, which is correlated among firms, cannot be insured by private companies. Premium differentiation may even have unfavorable consequences by raising unemployment duration

Dom Stabiliteitspact

Aanvankelijk vervulde het Stabiliteitspact een nuttige functie: duidelijke regels waarborgden de monetaire integratie. Door de vergrijzing en de conjuncturele verslechtering is het Pact aan herziening toe. Meer ruimte voor stabilisatiebeleid en het mede beschouwen van de pensioensituatie zijn belangrijker dan strikte naleving van het Pact omwille van geloofwaardigheid