The mechanisms of pedestrian slip on flooring contaminated with solid particles

Statistics by the UK Health and Safety Executive (HSE) suggest that slips, trips and falls account for up to one in three major workplace accidents. The vast majority of these accidents are the result of contaminant (fluid or solid) within the shoe-floor contact. Though the lubrication mechanisms for liquid contaminants within the contact are well understood, the same cannot be said for particulate contaminants. This paper considers the key parameters controlling friction in a shoe-floor contact contaminated with various particles of different diameters and shape factors and floors with different roughness values (Rz). Experiments were conducted using a Stanley Pendulum Tester, which is the floor friction tester recommended by the HSE. Results suggest that the adhesive friction is significantly affected by particulate contaminants, while the hysteretic component is not. Three lubrication mechanisms identified as sliding, shearing and rolling have been observed depending on floor roughness, particle size and shape factor and have been plotted in a simple map to predict behaviour

Deformations of asymptotically cylindrical G_2 manifolds

We prove that for a 7-dimensional manifold M with cylindrical ends the moduli space of exponentially asymptotically cylindrical torsion-free G_2 structures is a smooth manifold (if non-empty), and study some of its local properties. We also show that the holonomy of the induced metric of an exponentially asymptotically cylindrical G_2 manifold M is exactly G_2 if and only if its fundamental group is finite and neither M nor any double cover of M is homeomorphic to a cylinder.Comment: 31 pages, corrected proof of proposition 6.2

Jean-Luc Godard and the other history of cinema

Jean-Luc Godard's Histoire(s) du cinema (1988-1998) is a video work made up of visual and verbal quotations of hundreds of images and sounds from film history. But rather than simply telling (hi)stories of cinema, Godard makes a case for cinema as a tool for performing the work of history. This is partly because the film image, by virtue of always recording more of the real than was anticipated or intended, necessarily has history itself inscribed within its very fabric. It is also because montage, as the art of combining discrete elements in new ways in order to produce original forms, can be seen as a machine for realising historical thought. This thesis examines these ideas by discussing Godard's account of the role of cinema in the Second World War, and by analysing some of his recent work as examples of historical montage which attempt to criticise our current political climate through comparison with earlier eras. After a first chapter which sets out Godard's argument through an extensive commentary of Histoire(s) 1A and B, a second chapter discusses Godard's depiction of the invention of cinema and traces a complex argument about technology and historical responsibility around the key metaphorical figure of the train. Chapter 3 explores the ways in which Godard's historical approach to cinema allows him to maintain a critical discourse with regard to the geopolitical realities of late twentieth-century Europe (Germany, the Balkans), but also to the communications and business empires that have developed over the past few decades. A final chapter offers a detailed consideration of the nature of Godard's cinematic quotation and seeks to explicate the apocalyptic rhetoric of his late work. Aside from Histoire(s) du cinema, films discussed include Nouvelle Vague (1990), Allemagne neuf zero (1991), For Ever Mozart (1996) and Eloge de l'amour (2001)