A new methodology for hydrodynamic similarity in bubble columns

A new hypothesis has been proposed in this work for hydrodynamic similarity that can be subsequently used for scale‐up of bubble column reactors. The proposed hypothesis takes into account both global (by matching overall gas holdup) as well as local hydrodynamics (by matching time‐averaged radial profile/cross‐sectional distribution of gas holdup) to maintain similarity in two systems. The evaluation of proposed hypothesis has been accomplished utilising advanced diagnostic techniques such as gamma‐ray computed tomography (CT) and computer automated radioactive particle tracking (CARPT). In this work, we experimentally demonstrate that similarity based only on global hydrodynamics does not necessarily ensure similar mixing and turbulence in two systems. It is essential to maintain similar global as well as local hydrodynamics. The hydrodynamic similarity that can be obtained by matching the commonly used dimensionless groups was also evaluated at these experimental conditions.     

Crystallography and Structure–Property Relationships in 2,2′,2″,2′′′,4,4′,4″,4′′′,6,6′,6″,6′′′‐Dodecanitro‐1,1′ : 3′1″ : 3″,1′′′‐ Quaterphenyl (DODECA)

X‐ray crystallographic study of 2,2′,2″,2′′′,4,4′,4″,4′′′,6,6′,6″,6′′′‐dodecanitro‐1,1′ : 3′1″ : 3″,1′′′‐quaterphenyl (DODECA) has been carried out. Nonbonding interatomic distances of oxygen atoms inside of all the nitro groups are shorter than those corresponding to the intermolecular contact radii for oxygen. By means of the DFT B3LYP/6‐31(d, p) method a difference of 136 kJ mol⁻¹ between the X‐ray and DFT structures of DODECA was found. The bearer of the highest initiation reactivity in its molecule in solid phase should be the nitro group at 4′′′‐position, in contrast to those at 2′‐ or 2″‐positions in its isolated molecule. The most reactive nitro group in the DODECA molecule can be well specified by the relationship between net charges on nitro groups and charges on their nitrogen atoms, both of them for the X‐ray structure. The ¹⁵N chemical shift, corresponding to this nitro group for the initiation by impact and shock, correlates very well with these shifts of the reaction centers of the other six “genuine” polynitro arenes.     

Evolving Patterns: Correlated Systems of Interaction

Over the last four decades, the onset of computation has enabled architects and designers to employ generative patterns in their exploration of emergent social, material and spatial systems. Theodore Spyropoulos provides an overview of the field and discusses how it has been developed by the Design Research Lab (DRL) at the Architectural Association into an ‘Adaptive Ecologies’ agenda. In the context of parametric urbanism, the DRL has explored models of living through behavioural patterns found in nature, examining the role of the singular and the collective. Copyright © 2009 John Wiley & Sons, Ltd.     

Information Modelling as a Paradigm Shift

Building information modelling (BIM) is not just a change in software or skills sets, it requires a paradigm shift. Dennis Shelden , Chief Technology Officer of Gehry Technologies, outlines the more ‘fundamental, subtle and profound decisions’ on the road to BIM. It is necessary to fully consider not only the impacts both ‘upstream’ and ‘downstream’ from the conventional design phase, but also the possible creative restrictions as there is a potential trade-off that comes with the emphasis on collaborative processes. Copyright © 2009 John Wiley & Sons, Ltd.     

Exit Ltd

For London-based editor, author and curator Shumon Basar , The Temple of Janus Revisited by Exit Ltd is an effective critique of post-9/11 politics and culture. A virtual re-enactment of the Roman Temple of Janus in Washington DC, it evokes the imminent collapse of the American Empire. Copyright © 2009 John Wiley & Sons, Ltd.     

Proto-Design: Architecture's Primordial Soup and the Quest for Units of Synthetic Life

At the Massachusetts Institute of Technology (MIT), Neri Oxman is engaged on the Material-Based Computation project. It takes an approach that can be regarded as analogous to protocells. It places a similar emphasis on material properties as intermediary agents for the built environment, containing the information for behaviour and evolution. Here she outlines three methods that define her research. Copyright © 2011 John Wiley & Sons, Ltd.     

The True Counterfeits of Banksy: Radical Walls of Complicity and Subversion

Tattoo or consummate object of consumption? Banksy's artwork has an uneasy status. It simultaneously has the power to subvert, questioning the conventions of the art world while potentially colluding with it. Eva Branscome explores the paradox of Banksy in the light of Post-Modernism. Copyright © 2011 John Wiley & Sons, Ltd.     

Qualitative performance assessment of semiconductor switching device,converter and generator candidates for 10 MW offshore wind turbine generators

This paper investigates the possibilities of viable power electronics converters, semiconductor switching devices and electric machines for 10 MW variable‐speed wind turbine generators. The maximum rated power of existing wind turbine configurations is in the range of 6 MW. The proposed alternatives are compared against several technical and economical factors, and their advantages over the present wind turbines are highlighted. A comprehensive performance comparison of modern power semiconductor devices, their electrical characteristics and the key differentiators among them are presented. The power electronics converters considered include all commercially available multilevel voltage source and current source converters as well as the opportunities offered by power electronics building block‐based design. The factors used for the comparison include the converter power range, capacitor voltage balancing, common mode voltage and current, electromagnetic interference emissions, fault ride‐through capability, reliability, footprint, harmonic performance, efficiency and losses, component count, risk of torsional vibration by the harmonics and inter‐harmonics, complexity, ease of back‐to‐back operation and filtering requirements. For the electric machines, this study concentrates on high‐temperature superconducting machines, multi‐phase induction machines and permanent magnet synchronous machines. These machines are compared against existing wind generator technologies in terms of their power range, torque density, efficiency, fault ride‐through capability, reliability, footprint, harmonic performance, ease of fault detection, excitation control, noise and vibration signature, oscillation damping, gearbox requirement, cost and the size of the associated converter. Copyright © 2010 John Wiley & Sons, Ltd.