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Urban symbiosis is a strategy to create a more efficient metabolism of cities. However, urban symbiosis requires the integration of different systems, which is hard to achieve. Actors involved in existing systems can hardly develop ‘the bridges’ that are required to connect the thus far unrelated worlds of pre-existing systems. This paper analyses two cases of urban symbiosis and focusses on the process of building new actor networks. Urban symbiosis projects are generally complex and involve various stakeholders. The authors conclude that the introduction of additional actors or an additional institutional framework might be an effective means to create bridges between actors that could facilitate a more efficient metabolism of cities.

Background. Laws that enable a circular economy (CE) are being enacted globally, but reliable standardized and digitized CE data about products is scarce, and many CE platforms have differing exclusive formats. In response to these challenges, the Ministry of The Economy of Luxembourg launched the Circularity Dataset Standardization Initiative to develop a globalized open-source industry standard to allow the exchange of standardized data throughout the supply cycle, based on these objectives: (a) Provide basic product circularity data about products. (b) Improve circularity data sharing efficiency. (c) Encourage improved product circularity performance. A policy objective was to have the International Organization for Standardization (ISO) voted to create a working group. Methods. A state-of-play analysis was performed concurrently with consultations with industry, auditors, data experts, and data aggregation platforms. Results. Problem statements were generated. Based on those, a solution called Product Circularity Data Sheet (PCDS) was formulated. A proof of concept (POC) template and guidance were developed and piloted with manufacturers and platforms, thus fulfilling objective (a). For objective (b), IT ecosystem requirements were developed, and aspects are being piloted in third party aggregation platforms. Objective (c) awaits implementation of the IT ecosystem. The policy objective related to the ISO was met. Conclusions and future research. In order to fully test the PCDS, it is necessary to: conduct more pilots, define governance, and establish auditing and authentication procedures.

Abstract In this paper, steady segregation and slugging experiments are presented which have been carried out with a binary large-particle system representing the ash—coal/sorbent mixture in a fluidized-bed coal combustor. The slugging beds are characterized by dimensionless slug parameters which are obtained from visual bed-height measurements. The influence of the superficial gas velocity and the bed diameter on the extent of particle segregation is investigated. It is shown that a critical bed diameter exists above which segregation is nil. A simple segregation model is introduced proceeding with a proposed mechanism of segregation in slugging gas fluidized beds, which is based upon the visual observed flow of particles. The segregating particle distribution is characterized by one ‘Peclet-like’ dimensionless number, which is the ratio between the net particle convective and segregating flows and the dispersive solids flow in the bed.

Aerodynamic experiments have been executed in the wind tunnel and on a wind turbine blade to measure the impact of roughness on the airfoil characteristics and the associated effect on rotor performance and to establish the transition location on a rotating blade. The wind tunnel tests have been performed in the low-speed, low-turbulence wind tunnel of TUDelft. The wind turbine tests were carried out at ECN’s Wind Turbine Test Site. Roughness simulation material has been installed on the airfoil leading edge to measure the impact on airfoil performance. Microphones were mounted on the airfoil surface to detect the boundary layer laminar to turbulent transition position both on the wind tunnel model and on the wind turbine blade.

If Genetic Modification is to be accepted as a sustainable technological development its social, ecological and economical impacts must be understood. One important tool in determining the environmental and human risks of a technological development such as Genetical Modification (GM), is the Quantitative Risk Analysis (QRA). QRA can quantify the risks of a new technology, so that the society can make a choice whether the benefits outweigh the risks. Only if the risk of a new technological development is very small and acceptable, can it be sustainable. One of the main risks from GMOs is the spread of their genes through Gene Flow into wild populations causing genetic pollution and potentially ecosystem disruption. The current QRA is based on mass flow models. It does not consider the fact that law of conservation of mass does not hold for genes, which are essentially information. QRA also dos not take the imbedded open feedback loops present in life forms, i.e. the ability to self-amplify and reproduce, into consideration. Because of these shortcomings, the current risk assessment tools are probably inadequate to answer the question whether Genetic Modification is a sustainable technological development. Next to the lack of scientific knowledge about the impacts, there is a lack of societal acceptance of GM. Part of the reason for the lack of acceptance is the unacceptability of the tools for risk prediction. There is a need for a risk analysis tool that is both acceptable and able to describe key aspects of life. Agent Based Models (ABMs) are a candidate modeling framework for such a tool because they are isomorphic to living organisms. Furthemore, they are intuitive and easy to understand, forming a basis for societal acceptance. By defining evolutionary processes and plant entities in Agent terms an Agent Based Model called GeneScape has been developed. The model explicitly describes Plants as entities with states and interactions. Plants populate a geometry, the Field, through which the environment, The ...

ABSTRACTThe flow in the meridian plane of a high aspect ratio vertical‐axis wind turbine (VAWT) can be described as two dimensional. The wake that is generated by the VAWT in a two‐dimensional flow consists of shed vorticity and is a result of the temporal variation of bound circulation on the blades, following Kelvin's theorem. The strength and location of the vorticity that is produced by the VAWT in a two‐dimensional flow are thus independent of the average bound circulation on the blade. Two independent computational models—a potential flow panel model and a method that is based on the vorticity–velocity formulation of the Navier–Stokes equations—have been used to show that the VAWT can produce the same power for different azimuthal distributions of the blade aerodynamic loading. It is thus demonstrated that the instantaneous blade aerodynamic loading and the power conversion of a VAWT are decoupled. This observation has, potentially, significant impact on the design of the VAWT and reopens the research on asymmetric blade shapes in order to optimize the performance of this turbine configuration. Copyright © 2013 John Wiley & Sons, Ltd.

Performing accurate numerical simulations of molten salt reactors is challenging, especially in case of fast-spectrum designs, due to the unique physics phenomena characterizing these systems. The limitations of codes traditionally used in the nuclear community often require the development of novel high-fidelity multi-physics tools to advance the design of these innovative reactors. In this work, we present the most recent code developed at Delft University of Technology for multi-physics simulations of liquid-fueled fast reactors. The coupling is realized between an incompressible RANS model and an SN neutron transport solver. The models are implemented in two in-house codes, based on the discontinuous Galerkin Finite Element discretization, which guarantees high-quality of the solution. We report and discuss the results of preliminary simulations of the Molten Salt Fast Reactor at steady-state and during a Total Loss of Power transient. Results prove our code has capabilities for steady-state and transient analysis of non-moderated liquid-fueled reactors.