CONTEST : a Controllable Test Matrix Toolbox for MATLAB

Large, sparse networks that describe complex interactions are a common feature across a number of disciplines, giving rise to many challenging matrix computational tasks. Several random graph models have been proposed that capture key properties of real-life networks. These models provide realistic, parametrized matrices for testing linear system and eigenvalue solvers. CONTEST (CONtrollable TEST matrices) is a random network toolbox for MATLAB that implements nine models. The models produce unweighted directed or undirected graphs; that is, symmetric or unsymmetric matrices with elements equal to zero or one. They have one or more parameters that affect features such as sparsity and characteristic pathlength and all can be of arbitrary dimension. Utility functions are supplied for rewiring, adding extra shortcuts and subsampling in order to create further classes of networks. Other utilities convert the adjacency matrices into real-valued coefficient matrices for naturally arising computational tasks that reduce to sparse linear system and eigenvalue problems

Processing plant location studies II: Policy alternatives for New Zealand wool selling centres

The nature of the general facility location problem has been discussed previously by McCarthy, Rodgers & Higham and a method of solution outlined. The present paper aims to extend the solution technique so that a number of low cost solutions with differing spatial characteristics are generated. This permits entrepreneurs or policy makers to choose among the alternatives. The facility location problem can be stated as the determination of the number, size and location of a certain type of facility in order to satisfy the demand for the services provided; the "goodness" of any solution, relative to others, is measured in terms of some effectiveness criterion. For example one problem reported extensively in the agricultural economics literature is the determination of the number, size and location of agricultural commodity processing plants (freezing works, wool selling centres, grain storage depots), so that the sum of total transport (assembly plus distribution) costs and total processing costs are minimised. Another general type of problem receiving attention in applied operations research relates to the number, size and location of public emergency services (for example ambulance and hospital services). Here, some measure of cost effectiveness is optimised Empirical studies include those of Fitzsimmons, Savas and Volz. This paper is concerned primarily with processing and has two major sections. The first section outlines methodology and discusses Monte Carlo and "forcing" extensions of standard solutions. The second section applies such procedures to the New Zealand wool selling centres' location problem

Loop integration results using numerical extrapolation for a non-scalar integral

Loop integration results have been obtained using numerical integration and extrapolation. An extrapolation to the limit is performed with respect to a parameter in the integrand which tends to zero. Results are given for a non-scalar four-point diagram. Extensions to accommodate loop integration by existing integration packages are also discussed. These include: using previously generated partitions of the domain and roundoff error guards.Comment: 4 pages, 3 figures, revised, contribution to ACAT03 (Dec. 2003

Communicability across evolving networks

Many natural and technological applications generate time ordered sequences of networks, defined over a fixed set of nodes; for example time-stamped information about ‘who phoned who’ or ‘who came into contact with who’ arise naturally in studies of communication and the spread of disease. Concepts and algorithms for static networks do not immediately carry through to this dynamic setting. For example, suppose A and B interact in the morning, and then B and C interact in the afternoon. Information, or disease, may then pass from A to C, but not vice versa. This subtlety is lost if we simply summarize using the daily aggregate network given by the chain A-B-C. However, using a natural definition of a walk on an evolving network, we show that classic centrality measures from the static setting can be extended in a computationally convenient manner. In particular, communicability indices can be computed to summarize the ability of each node to broadcast and receive information. The computations involve basic operations in linear algebra, and the asymmetry caused by time’s arrow is captured naturally through the non-mutativity of matrix-matrix multiplication. Illustrative examples are given for both synthetic and real-world communication data sets. We also discuss the use of the new centrality measures for real-time monitoring and prediction

Image-based tracking technique assessment and application to a fluid–structure interaction experiment

This work analyses the accuracy and capabilities of two image-based tracking techniques related to digital image correlation and the Lucas–Kanade optical flow method, with the subsequent quantification of body motion in a fluid–structure interaction experiment. A computer-controlled shaker was used as a benchmark case to create a one-dimensional oscillatory target motion. Three target frequencies were recorded. The measurements obtained with a low-cost digital camera were compared to a high-precision motion tracking system. The comparison was performed under changes in image resolution, target motion and sampling frequency. The results show that, with a correct selection of the processing parameters, both tracking techniques were able to track the main motion and frequency of the target even after a reduction of four and five times the sampling frequency and image resolution, respectively. Within this good agreement, the Lucas–Kanade technique shows better accuracy under tested conditions, achieving up to 15.6% of lower tracking error. Nevertheless, the achievement of this higher accuracy is highly dependent on the position of the selected initial target point. These considerations are addressed to satisfactorily track the response of a wall-mounted cylinder subjected to a range of turbulent flows using a single camera as the measuring device

Information mobility in complex networks

The concept of information mobility in complex networks is introduced on the basis of a stochastic process taking place in the network. The transition matrix for this process represents the probability that the information arising at a given node is transferred to a target one. We use the fractional powers of this transition matrix to investigate the stochastic process at fractional time intervals. The mobility coefficient is then introduced on the basis of the trace of these fractional powers of the stochastic matrix. The fractional time at which a network diffuses 50% of the information contained in its nodes (1/ k50 ) is also introduced. We then show that the scale-free random networks display better spread of information than the non scale-free ones. We study 38 real-world networks and analyze their performance in spreading information from their nodes. We find that some real-world networks perform even better than the scale-free networks with the same average degree and we point out some of the structural parameters that make this possible

What is the current state of debate around the use of contextualised admissions for undergraduate admissions? A review of the current stakeholder perspective

This is the author accepted manuscript. The final version is available from Taylor & Francis (Routledge) via the DOI in this record.Higher Education Institutions in England are an integral part of the government’s social mobility strategy. Contextualisation of undergraduate admissions decisions has emerged as a key tool towards progressing social mobility objectives. The present paper builds on our previous 2013 research by describing findings from 15 qualitative interviews with stakeholders in contextualised admissions. Stakeholders were drawn from government, non-governmental and third sector bodies including those representing the voice of schools and young people. We find that data challenges continue to be a main barrier to the application of contextual admissions. Respondents thought that more consistency and transparency between universities would be helpful to assist applicants and those who support them to better understand contextual data use in undergraduate admissions. Views are divided about whether differential admissions offers represent the most important application of contextual data. Respondents saw potential for using contextual data beyond admissions for supporting students at university and into further study or employment.The Access Projec

'The show must go on': Event dramaturgy as consolidation of community

Event dramaturgy and cultural performance have not been examined in the literature from a strategic standpoint of fostering the social value of events. Thus, the purpose of this study was to explore the case of the Water Carnival, a celebratory event in a rural community of Southwest Texas, demonstrating the essence of this event as a symbolic social space, wherein event participants instantiate a shared and valued sense of community. A hermeneutical approach was employed, interpreting the event and its symbolisms as a text, combined with findings from ethnographic fieldwork, including participant observation, in-depth interviews and analysis of archival documents. The study examines the ways that dramaturgy in the Water Carnival helps frame the ongoing public discourse for community improvement and enhances social capital. The implications of the study for social leverage of events are discussed. It is suggested that a foundation for strategic social planning is the understanding of events as symbolic social spaces and their embeddedness in community development, which can be accomplished when events are pertinent to public discourse, address community issues, represent an inclusive range of stakeholders, and promote cooperation

Solution of the Multi-Channel Anderson Impurity Model: Ground state and thermodynamics

We present the solution of the SU(N) x SU(M) Anderson impurity model using the Bethe-Ansatz. We first explain what extensions to the formalism were required for the solution. Subsequently we determine the ground state and derive the thermodynamics over the full range of temperature and fields. We identify the different regimes of valence fluctuation at high temperatures, followed by moment formation or intrinsic mixed valence at intermediate temperatures and a low temperature non-Fermi liquid phase. Among other things we obtain the impurity entropy, charge valence and specific heat over the full range of temperature. We show that the low-energy physics is governed by a line of fixed points. This describes non-Fermi-liquid behavior in the integral valence regime, associated with moment formation, as well as in the mixed valence regime where no moment forms.Comment: 28 pages, 8 figures, 1 tabl

Projection methods in conic optimization

There exist efficient algorithms to project a point onto the intersection of a convex cone and an affine subspace. Those conic projections are in turn the work-horse of a range of algorithms in conic optimization, having a variety of applications in science, finance and engineering. This chapter reviews some of these algorithms, emphasizing the so-called regularization algorithms for linear conic optimization, and applications in polynomial optimization. This is a presentation of the material of several recent research articles; we aim here at clarifying the ideas, presenting them in a general framework, and pointing out important techniques