Dynamic X-ray radiography for the determination of foamed bitumen bubble area distribution

Foam bitumen is highly efficient in wetting and coating the surface of mineral aggregate at lower temperature. In order to improve understanding and characterization of the bitumen foam, X-ray radiography was used to study the formation and decay of bitumen foam in 2D representation. Image segmentation analysis was used to determine the foam bubble size distribution. In addition, the main parameters influencing foam bitumen formation, water content, and temperature were also investigated. The results demonstrate the influence of the water content on morphology and expansion of foam bitumen bubbles. Adding more water in the foaming process leads to quick collapse of bubbles and intensifies coalescence of foam bitumen. Higher temperatures produces larger bubbles at early foaming stage compared to lower temperature. Moreover the morphology of bubble formation depends on the types of bitumen used. An exponential function has been implemented to represent the bubble area distribution.     

Environmentally Sustainable Construction: Knowledge and Learning in London Planning Departments

Environmentally sustainable construction is now recognised as a significant element of the broader sustainable development agenda and planners are being called upon to play a role in delivering more sustainable patterns of construction and development. This puts particular demands on the knowledge resources of planners since knowledge is implicated in the power relations between planners and developers. This paper examines the interrelationship between knowledge of environmentally sustainable construction and practice in planning departments. Drawing on a survey of and interviews with planners in London, it discusses the construction of knowledge within the dynamics of planning organisations and the potential for learning to promote a more sustainable built environment. Wenger's concept of communities of practice frames the analysis, alongside consideration of the translation of knowledge into bureaucratic and usable forms and the role of knowledge brokers in this process.