Application of topological conservation to model key features of zero-torque multi-ply yarns

During yarn formation by ring spinning, fibres are bent into approximately helical shapes and torque or twist-liveliness is created. The yarn torque causes yarn instability, manifested as snarling or entanglements, and this instability must be controlled during manufacturing processes. Generally, the torque depends on yarn geometric factors such as the yarn twist, linear density and the fibre properties. A practical solution to the problem of twist-liveliness is the formation of a two-fold yarn. This twisting or plying process produces a yarn structure where the energy of the system is determined by purely geometrical constraints of the plied structure and consequently when an energy minimum is reached the plied yarn obtained from the process is torsionally balanced and torque-free. In the present paper, the stability of plied textile yarns will be evaluated using the Topological Conservation law (Fuller, F. B., 1971, Proc.Nat. Acad. Sci. USA, 68, 815–819.) developed to study the post-buckling behaviour of twisted rods by Van der Heijden et al. (Int. J. Mech. Sci., 45, 161–196, 2003).The present work considers the equilibrium configuration of a series of multi-ply twisted yarns (2, 4, and 6 strands) of finite length. Several structural and mechanical properties are highlighted: (i) the influence of structural properties (the number of strands, the strand linear density and strand twist) and the ratio of the torsional and bending stiffnesses of the strands on the balance point in multi-ply yarns. The topological invariant of the twisted yarn (link) is used to calculate the ply and strand properties (writhe) and compared with experimental results obtained at CSIRO. The inter-strand pressure between strands of a multi-ply yarn, a feature of interest for fibre interactions in yarn structures, is also calculated at the balance situation across a range of structural and mechanical conditions

Disintegrated development at the rural–urban fringe: Re-connecting spatial planning theory and practice

The spaces where countryside meets town are often amongst society's most valued and pressured places which together form the rural–urban fringe (RUF). A ‘messy’ yet opportunistic space in policy and decision making processes, the RUF remains confused and ‘disintegrated’ lacking sufficient understanding and explicit attention for sustainable management as places in their own right. This paper exposes the scope, nature and reasons leading towards policy disintegration within the RUF with critical attention on the separate lenses of the Ecosystem Approach and Spatial Planning frameworks reflecting a marked natural and built environment divide. Using research funded by the Rural Economy and Land Use programme, three ‘bridging’ concepts were identified within which improved integration is explored: Time, Connections and Values. Using team member thoughtpieces and workshops, together with visioning exercises in two rural–urban fringes, a series of narratives are presented within which the RUF opportunity is re-discovered set within a hybridised theory of spatial and environmental planning. In so doing the paper challenges established economic and planning models of urban development and expansion with more holistic ideas and approaches. One size-fits-all solutions such as greenbelts, regionalism or localism are rejected within an approach that champions multi-scalar and sectoral perspectives set within a governance framework that achieves social and economic well-being through maintaining and enhancing ecosystem functions and services. We conclude by arguing that policy strands within environment and planning must be better connected allowing the RUF to be developed as an opportunity space for testing and experimentation