Aromatic Copolyester-based Nano-biocomposites: Elaboration, Structural Characterization and Properties

Biodegradable polymers are one of the most promising ways to replace non-degradable polymers. But, to be a real alternative to classical synthetic polymers and find applications, biopolymer (biodegradable polymer) properties have to be enhanced. Nano-biocomposites, which are obtained by incorporation of nanofillers into a biomatrix, are an interesting way to achieve these improvements. Modified and unmodified montmorillonites have been introduced into a biodegradable aromatic copolyester, poly(butylene adipate-co-terephthalate) (PBAT). Structural characterization, thermal and mechanical tests have been carried out to understand better the relations between the nanofillers structuring and the final nano-biocomposite properties. Main results show that clay incorporation and the obtained intercalated structures improve PBAT properties (enhanced thermal stability, increased stiffness) and thus may increase the attractiveness of this biopolymer.     

Laboratory scale analysis of the influence of different heat transfer mechanisms on liquid nitrogen vaporization rate

The prediction of the potential hazards associated to accidental liquefied natural gas (LNG) spills has motivated a number of different studies including experimental and numerical approaches. Most of these studies focus on dispersion predictions, however there is limited information regarding source term of it: liquid spill and vaporization. There is a need of further improvements on the understanding of these phenomena and the quantification of the most important parameters that can affect them.The vaporization of cryogenic liquids is governed by the heat transfer phenomena including conduction, convection and thermal radiation mechanisms. The present work investigates the contribution of each of these heat transfer modes to the vaporization rate of cryogenic liquid nitrogen (LN₂) contained in a Dewar flask using well controlled and instrumented laboratory scale experiments. LN₂ vaporization rate was measured with individually controllable contributions from convective (generated by an electric fan) and thermal radiative (generated by light bulb) heat transfer in the presence of a baseline conductive heat transfer rate.In both cases of convection and radiation analysis the experimental study showed that they can play a significant role in the vaporization rate of LN₂. It was observed that the radiative heat absorbed by the LN₂ during the vaporization experiment represents only 50%–65% of the incident radiation that would reach the LN₂ pool surface if no vapour was present. Convective heat transfer generated by the fan was shown to have had the most significant contribution to the total heat transfer. As expected, this contribution was significantly higher than the one from bulb radiation. The experimental data also showed that the liquid level in the Dewar play a key role in the resulting amount of convective heat transfer. This could be attributed to the fact that lower liquid level the side walls of the Dewar were high enough to hold a layer of vapour and limit air motion directly above the liquid surface, thus limiting the heat transfer by convection.     

Legitimate adaptive flood risk governance beyond the dikes: the cases of Hamburg,Helsinki and Rotterdam

It has recently been recommended that a shift from traditional flood prevention to more adaptive strategies is made, focusing on the reduction in and recovery from flood impacts as a means to improve resilience to climate impacts. This shift has had implications for the public–private divide in adaptive flood risk governance. In an urban context, it means that private actors such as developers and residents come into play, necessitating governance arrangements which cross the public–private divide. The division of responsibilities for water safety between the public and private sectors affects the way legitimacy is gained for these arrangements and raises new legitimacy issues. The paper offers an analysis of public and private responsibilities in adaptive flood risk governance arrangements, as well as of the legitimacy of the arrangements in the light of the public–private divide. A comparative case study is presented for three urban regeneration projects in un-embanked areas in Hamburg, Germany, Helsinki, Finland, and Rotterdam, the Netherlands, where adaptive strategies have been applied. The results show that network arrangements with joint public–private responsibilities use direct forms of participation and deliberation, but that these do not necessarily lead to more legitimate arrangements in the eyes of stakeholders as is often suggested in the literature. Both network and more public hierarchical arrangements can be perceived as quite legitimate under certain conditions.