International collaboration clusters in Africa

Recent discussion about the increase in international research collaboration suggests a comprehensive global network centred around a group of core countries and driven by generic socio-economic factors where the global system influences all national and institutional outcomes. In counterpoint, we demonstrate that the collaboration pattern for countries in Africa is far from universal. Instead, it exhibits layers of internal clusters and external links that are explained not by monotypic global influences but by regional geography and, perhaps even more strongly, by history, culture and language. Analysis of these bottom-up, subjective, human factors is required in order to provide the fuller explanation useful for policy and management purposes.Comment: 12 pp, 5 Figs including map links to viewe

Repentir: Digital exploration beneath the surface of an oil painting

Repentir is a mobile application that employs marker-less tracking and augmented reality to enable gallery visitors to explore the under drawing and successive stages of pigment beneath an oil painting's surface. Repentir recognises the position and orientation of a specific painting within a photograph and precisely overlays images that were captured during that painting's creation. The viewer may then browse through the work's multiple states and closely examine its painted surface in one of two ways: sliding or rubbing. Our current prototype recognises realist painter Nathan Walsh's most recent work, "Transamerica". Repentir enables the viewer to explore intermediary stages in the painting's development and see what is usually lost within the materially additive painting process. The prototype offers an innovative approach to digital reproduction and provides users with unique insights into the painter's working method

Echo State Networks Trained by Tikhonov Least Squares are L2 Approximators of Ergodic Dynamical Systems

Echo State Networks (ESNs) are a class of single-layer recurrent neural networks with randomly generated internal weights, and a single layer of tuneable outer weights, which are usually trained by regularised linear least squares regression. Remarkably, ESNs still enjoy the universal approximation property despite the training procedure being entirely linear. In this paper, we prove that an ESN trained on a sequence of observations from an ergodic dynamical system (with invariant measure ) using Tikhonov least squares regression against a set of targets, will approximate the target function in the norm. In the special case that the targets are future observations, the ESN is learning the next step map, which allows time series forecasting. We demonstrate the theory numerically by training an ESN using Tikhonov least squares on a sequence of scalar observations of the Lorenz system

Embedding and approximation theorems for echo state networks

Echo State Networks (ESNs) are a class of single layer recurrent neural networks that have enjoyed recent attention. In this paper we prove that a suitable ESN, trained on a series of measurements of an invertible dynamical system, induces a C1 map from the dynamical system's phase space to the ESN's reservoir space. We call this the Echo State Map. We then prove that the Echo State Map is generically an embedding with positive probability. Under additional mild assumptions, we further conjecture that the Echo State Map is almost surely an embedding. For sufficiently large, and specially structured, but still randomly generated ESNs, we prove that there exists a linear readout layer that allows the ESN to predict the next observation of a dynamical system arbitrarily well. Consequently, if the dynamical system under observation is structurally stable then the trained ESN will exhibit dynamics that are topologically conjugate to the future behaviour of the observed dynamical system. Our theoretical results connect the theory of ESNs to the delay-embedding literature for dynamical systems, and are supported by numerical evidence from simulations of the traditional Lorenz equations. The simulations confirm that, from a one dimensional observation function, an ESN can accurately infer a range of geometric and topological features of the dynamics such as the eigenvalues of equilibrium points, Lyapunov exponents and homology groups.Comment: 24 pages, 9 figure

A max-plus approach to incomplete Cholesky factorization preconditioners

We present a new method for constructing incomplete Cholesky factorization preconditioners for use in solving large sparse symmetric positive-definite linear systems. This method uses max-plus algebra to predict the positions of the largest entries in the Cholesky factor and then uses these positions as the sparsity pattern for the preconditioner. Our method builds on the max-plus incomplete LU factorization preconditioner recently proposed in [J. Hook and F. Tisseur, Incomplete LU preconditioner based on max-plus approximation of LU factorization, MIMS Eprint 2016.47, Manchester, 2016] but applied to symmetric positive-definite matrices, which comprise an important special case for the method and its application. An attractive feature of our approach is that the sparsity pattern of each column of the preconditioner can be computed in parallel. Numerical comparisons are made with other incomplete Cholesky factorization preconditioners using problems from a range of practical applications. We demonstrate that the new preconditioner can outperform traditional level-based preconditioners and offer a parallel alternative to a serial limited-memory based approach

Interaction design for live performance

PhD Thesis Multimedia item accompanying this thesis to be consulted at Robinson LibraryThe role of interactive technology in live performance has increased substantially in recent years. Practices and experiences of existing forms of live performance have been transformed and new genres of technology-­‐mediated live performance have emerged in response to novel technological opportunities. Consequently, designing for live performance is set to become an increasingly important concern for interaction design researchers and practitioners. However, designing interactive technology for live performance is a challenging activity, as the experiences of both performers and their audiences are shaped and influenced by a number of delicate and interconnected issues, which relate to different forms and individual practices of live performance in varied and often conflicting ways. The research presented in this thesis explores how interaction designers might be better supported in engaging with this intricate and multifaceted design space. This is achieved using a practice-­‐led methodology, which involves the researcher’s participation in both the investigation of, and design response to, issues of live performance as they are embodied in the lived and felt experiences of individual live performers’ practices during three interaction design case studies. This research contributes to the field of interaction design for live performance in three core areas. Understandings of the relationships between key issues of live performance and individual performers’ lived and felt experiences are developed, approaches to support interaction designers in engaging individual live performers’ lived and felt experiences in design are proposed and innovative interfaces and interaction techniques for live performance are designed. It is anticipated that these research outcomes will prove directly applicable or inspiring to the practices of interaction designers wishing to address live performance and will contribute to the ongoing academic discourse around the experience of, and design for, live performance.Engineering and Physical Sciences Research Council

“More than just Space” : Designing to Support Assemblage in Virtual Creative Hubs

This paper aims to understand interactions at creative hubs, and how this understanding can be used to inform the design of virtual creative hubs – i.e., social-technical infrastructures that support hub-like interactions amongst people who aren’t spatially or temporally co-located. We present findings from a qualitative field study in UK creative hubs, in which we conducted seventeen observations and ten interviews in three sites. Our findings reveal a range of key themes that define interactions within creative hubs: smallness of teams; neutrality of the hubs; value of the infrastructure; activities and events; experience sharing; and community values and rules. These interactions together form a network and elements that influence one another to make a creative hub more than just physical space. We employ the concept of Assemblage introduced by Deleuze and Guattari to explore this network of interactions and, in doing so, reveal implications for the design of virtual creative hubs that seek to replicate them