The intuitions of higher dimensional algebra for the study of structured space

Higher dimensional algebra frees mathematics from the restriction to a purely linear notation, in order to improve the modelling of geometry and so obtain more understanding and more modes of computation. It gives new tools for noncommutative, higher dimensional, local to global problems, through the notion of «algebraic inverse to subdivision». We explain the way these ideas arose for the writters, in extending first the classical notion of abstract group to abstract groupoid, in which composition is only partially defined, as in composing journeys, and which brings a spatial component to the usual group theory: An example from knot theory is used to explain how such algebra can be used to describe some structure of a space. The extension to dimension 2 uses compositions of squares in two directions, and the richness of the resulting algebra is shown by some 2-dimensional calculations. The difficulty of the jump from dimension 1 to dimension 2 is also illustrated by the comparison of the commutative square with the commutative cube-discussion of the latter requires new ideas. The importance of category theory is explained, and a range of current and potential applications of higher dimensional algebra indicated.     

Negotiating In/visibility: The Political Economy of Lesbian Activism and Rights Advocacy

Efforts to address HIV/AIDS have brought new opportunities and resources to LGBT (lesbian, gay, bisexual, transgender) activism in many parts of the developing world. However, increased attention in terms of both political opportunities and economic resources is uneven across the diverse population of LGBT peoples and activists. Lesbian activists have reaped far fewer benefits than their gay men counterparts. Building on existing approaches to movement visibility and invisibility, we posit a ‘political economy of in/visibility’ to analyse lesbian activism in China and Myanmar, where activists face particularly restrictive political and economic conditions. Rather than focus on visibility as a movement pre‐condition, objective or strategy, we examine the sources of in/visibility and their interactions with activists’ agency; in/visibility emerges from political and economic conditions, but is continuously reshaped by activists who negotiate them. We demonstrate that, despite challenges, lesbian activists respond in ways that help advance LGBT rights advocacy broadly, sometimes even with tactics that their more visible gay counterparts avoid. These interactions subsequently influence the conditions that shape in/visibility. Investigating the political economy of in/visibility, therefore, has significant implications for understanding not only lesbian activism, but also LGBT advocacy and collective mobilization, especially under politically and economically restrictive conditions.     

Capacity Design of Coupled RC Walls

Capacity design aims to ensure controlled ductile response of structures when subjected to earthquakes. This article investigates the performance of existing capacity design equations for reinforced concrete coupled walls and then proposes a new simplified capacity design method based on state-of-the-art knowledge. The new method is verified through a case study in which a set of 15 coupled walls are subject to nonlinear time-history analyses. The article includes examination of the maximum shear force in individual walls in relation to the total maximum shear force in the coupled wall system, and subsequently provides recommendations for design.