Analysis of a moving mask approximation for martensitic transformations

In this work we introduce a moving mask approximation to describe the dynamics of austenite to martensite phase transitions at a continuum level. In this framework, we prove a new type of Hadamard jump condition, from which we deduce that the deformation gradient must be of the form $\mathsf{1} +\mathbf{a}\otimes \mathbf{n}$ a.e. in the martensite phase. This is useful to better understand the complex microstructures and the formation of curved interfaces between phases in new ultra-low hysteresis alloys such as Zn45Au30Cu25, and provides a selection mechanism for physically-relevant energy-minimising microstructures. In particular, we use the new type of Hadamard jump condition to deduce a rigidity theorem for the two well problem. The latter provides more insight on the cofactor conditions, particular conditions of supercompatibility between phases believed to influence reversibility of martensitic transformations

Plot-based urbanism : towards time-consciousness in place-making

Some of us have recently argued that what we still miss is the serious consideration of the factor of time in urbanism, or, in other words, a deeper "time conscious" approach (Thwaites, Porta, Romice, & Greaves, 2008). Inevitably, that means focusing on change as the essential dynamic of evolution in the built environment, which in turn leads to re-addressing concepts like control, self-organization and community participation. After time and change have been finally firmly placed at the centre stage, the whole discipline of urban planning and design, its conceptual equipment as well as its operational toolbox, reveals its weaknesses under a new light and calls for the construction of a different scenario. This paper poses the problem of this scenario in disciplinary terms, it argues about its premises and outlines its essential features. The scope of this paper is not to deliver a comprehensive model for a new approach to urban planning and design, but to set the right framework and rise the right questions so that we can start thinking of issues such as urban regeneration, informal settlements and massive urbanization, community participation and representation, beauty and humanity in space, in a different way