Choosing Colors for Geometric Graphs via Color Space Embeddings

Graph drawing research traditionally focuses on producing geometric embeddings of graphs satisfying various aesthetic constraints. After the geometric embedding is specified, there is an additional step that is often overlooked or ignored: assigning display colors to the graph's vertices. We study the additional aesthetic criterion of assigning distinct colors to vertices of a geometric graph so that the colors assigned to adjacent vertices are as different from one another as possible. We formulate this as a problem involving perceptual metrics in color space and we develop algorithms for solving this problem by embedding the graph in color space. We also present an application of this work to a distributed load-balancing visualization problem.Comment: 12 pages, 4 figures. To appear at 14th Int. Symp. Graph Drawing, 200

Mixed Reality Architecture: Concept, Construction, Use

Mixed Reality Architecture (MRA) dynamically links and overlays physical and virtual spaces. This paper investigates the topology of and the relationships between the components of MRA. As a phenomenon, MRA takes its place in a long history of technologies that have influenced conditions for social interaction as well as the environment we build around us. However, by providing a flexible spatial topology spanning physical and virtual environments it presents new opportunities for social interaction across electronic media. An experimental MRA is described that allowed us to study some of the emerging issues in this field. It provided material for the development of a framework describing virtual and physical spaces, the links between those and the types of mixed reality structure that we can envisage it being possible to design using these elements. We propose that by re-introducing a level of spatiality into communication across physical and virtual environments MRA will support everyday social interaction, and may convert digital communication media from being socially conservative to a more generative form familiar from physical space

Enter the Circle: Blending Spherical Displays and Playful Embedded Interaction in Public Spaces

Public displays are used a variety of contexts, from utility driven information displays to playful entertainment displays. Spherical displays offer new opportunities for interaction in public spaces, allowing users to face each other during interaction and explore content from a variety of angles and perspectives. This paper presents a playful installation that places a spherical display at the centre of a playful environment embedded with interactive elements. The installation, called Enter the Circle, involves eight chair-sized boxes filled with interactive lights that can be controlled by touching the spherical display. The boxes are placed in a ring around the display, and passers-by must “enter the circle” to explore and play with the installation. We evaluated this installation in a pedestrianized walkway for three hours over an evening, collecting on-screen logs and video data. This paper presents a novel evaluation of a spherical display in a public space, discusses an experimental design concept that blends displays with embedded interaction, and analyses real world interaction with the installation

Electrochemical growth of three-dimensionally ordered macroporous metals as photonic crystals

Over the last two decades three dimensionally ordered macroporous (3-DOM) materials have turned out to be very promising in many applications ranging from optics, plasmonics, to catalyst scaffolds. The thesis presents a systematic study on formation and characterisation of 3-DOM metals as photonic crystals. Metals are nearly perfect reflectors with low adsorption at microwave or millimetre wavelengths. Meanwhile they generally absorb visible light because of their negative imaginary part of the dielectric constant that could destroy the band gap in the visible though they. Howevers, for noble metals such as gold, silver and copper, considering the Drude-like behaviour, the adsorption will be small enough to achieve a complete photonic band gap for optical or even shorter wavelengths, with silver performing the best. In order to fabricate the 3-DOM metallic nanostructures, template-directed electrochemical deposition has been employed in which, initially a highly ordered film of submircon sized colloidal spheres is deposited on to electronically conducting substrates, for instance, indium-tin oxide (ITO) coated glass substrate, through evaporation-induced self-assembly; and subsequently it is infiltrated with metallic elements electrochemically reduced from corresponding electrolytes; fiannly removal of the colloidal templating film reveals a metallic film comprised of periodically arranged spherical voids. Field Emission Gun Scanning Electron Microscopy (FEGSEM) was used to examine the surface morphology and periodicity of the 3-DOM metallic films. It revealed that highly ordered structures are homogenous and uniform over a large scale for both the original colloidal templates and metallic inverse structures. However for silver electroplated from either silver thiosulfate or silver chlorate bath, voids in the template are fully infiltrated, including both the interstitial spaces between the colloidal spheres and any cracks between film domains, forming a complete solid network over large length scales; for copper the filling factors are strongly dependent on the bath chemistry and in copper sulfate bath isolated macroporous domains can be formed due to those in the cracks will be dissolved back to the solution while those reduced from copper glycerol bath resulted in fully infiltrated structures. Moreover, angle-resolved reflectance spectroscopy has further confirmed the three-dimensional periodicity and indicated the inverse structures have stop band properties in the visible wavelength region, consistent with variation in the effective refractive index of the films. In addition, surface enhanced Raman scattering (SERS) spectroscopy has been used to evaluate applications of the inverse metals as SERS-active substrates. SERS has nearly exclusively been associated with three noble metals copper, silver (by far the most important) and gold. The 3-DOM metallic thin films possess excellent features for SERS detection arising from their long range periodical void geometry, which gives significant enhancement to Raman intensity. Preliminary measurements have demonstrated the 3-DOM metallic structures are well suited for SERS enhancement. Series spectra from different points of each specimen have given reproducible intensities. Variables associated with Raman intensity such as pore size, dye concentration, and film thickness, have been tuned to achieve maximal enhancement for visible and near-IR wavelengths

Volumetric Untrimming: Precise decomposition of trimmed trivariates into tensor products

3D objects, modeled using Computer Aided Geometric Design tools, are traditionally represented using a boundary representation (B-rep), and typically use spline functions to parameterize these boundary surfaces. However, recent development in physical analysis, in isogeometric analysis (IGA) in specific, necessitates a volumetric parametrization of the interior of the object. IGA is performed directly by integrating over the spline spaces of the volumetric spline representation of the object. Typically, tensor-product B-spline trivariates are used to parameterize the volumetric domain. A general 3D object, that can be modeled in contemporary B-rep CAD tools, is typically represented using trimmed B-spline surfaces. In order to capture the generality of the contemporary B-rep modeling space, while supporting IGA needs, Massarwi and Elber (2016) proposed the use of trimmed trivariates volumetric elements. However, the use of trimmed geometry makes the integration process more difficult since integration over trimmed B-spline basis functions is a highly challenging task. In this work, we propose an algorithm that precisely decomposes a trimmed B-spline trivariate into a set of (singular only on the boundary) tensor-product B-spline trivariates, that can be utilized to simplify the integration process in IGA. The trimmed B-spline trivariate is first subdivided into a set of trimmed B\'ezier trivariates, at all its internal knots. Then, each trimmed B\'ezier trivariate, is decomposed into a set of mutually exclusive tensor-product B-spline trivariates, that precisely cover the entire trimmed domain. This process, denoted untrimming, can be performed in either the Euclidean space or the parametric space of the trivariate. We present examples on complex trimmed trivariates' based geometry, and we demonstrate the effectiveness of the method by applying IGA over the (untrimmed) results.Comment: 18 pages, 32 figures. Contribution accepted in International Conference on Geometric Modeling and Processing (GMP 2019

Exploring mischief and mayhem in social computing or: how we learned to stop worrying and love the trolls

In this paper, we explore the role of mischief as borderline socially acceptable behaviour within social computing applications. Mischievous activity pushes the boundaries of the implicit social contract present in all online social systems, and, we argue, is of vital importance understanding online social interactions. Using examples from games and other applications, we explore mischief as an act of appropriation, which reinterprets mechanics defined by developers in unexpected and sometimes upsetting ways. Although frequently interpreted as negative and anti-social behaviour, we argue that mischief serves a vital social role, and find surprising richness in the chaos

Research report 22: liveability in NDC areas: findings from six case studies

New Deal for Communities (NDC) is a key programme in the Government's strategy to tackle multiple deprivation by giving some of the poorest communities in the UK the resources to tackle their problems in an intensive and co-ordinated way. The programme, which began in 1998, has encouraged the development of partnerships between local people, community and voluntary organisations, public agencies, local authorities and business. These partnerships are working to tackle the problems of social exclusion and make a lasting improvement to their neighbourhood, with the active involvement of the local community. While different areas face different problems, the five main issues to be tackled by NDC partnerships are: worklessness; improving health; tackling crime; raising educational achievement; and housing and the physical environment. Sustainable Cities Research Institute is part of a national consortium carrying out the evaluation of NDC. The evaluation is led by Sheffield Hallam University and involves 14 UK research centres, universities, and private consultancy firms. Sustainable Cities staff involved with this work are Keith Shaw, who is the North East Region Co-ordinator (with responsibility for Hartlepool, Middlesbrough, Newcastle and Sunderland partnerships), and Gill Davidson, who is carrying out evaluation tasks in Middlesbrough. Also involved in this work at a regional level are staff members from the University's School of Politics, and from the University of Newcastle. The evaluation began with a scoping phase in October 2001. The evaluation is expected to continue in its current format until at least 2005, with annual evaluation reports being produced in 2003, 2004, and 2005. Sustainable Cities is also undertaking research for a series of case studies focusing on West Middlesbrough NDC; so far these have covered subjects including mainstreaming, involving hard-to-reach young people in regeneration, and liveability