Cycling’s Sensory Strategies: How Cyclists Mediate their Exposure to the Urban Environment

In this article, we focus on the many ways cyclists mediate their sensory exposure to the urban environment. Drawing on research in Hull, Hackney and Bristol during 2010 and 2011 for the Cycling Cultures research project, we describe a range of ‘sensory strategies’ enrolled by cyclists. Our research reveals how sensory strategies, such as using mobile audio devices, involve deliberate and finely tuned practices shaped by factors such as relaxation, motivation and location. This presents a contrast to media representations of the ‘iPod zombie cyclist’ who, plugged into a mobile audio device, lumbers insensitively and dangerously through the urban landscape. The article complicates the idea that sensory practices of listening and not-listening are two fixed and distinct ways of being in the urban environment. We suggest that considering the sensory strategies of cyclists opens up a new terrain for thinking about less easily represented, uncertain and fleeting intersections of mobility, place and the senses. Ultimately, we argue that an analysis of cycling’s sensory strategies might enrich our understanding of mobility cultures by operating to reconnect a range of mobile citizens with the broader messy and less easily controllable sensory landscape. This has implications both for understanding cycling as a sensory practice and for thinking about how the sensory dimensions of other mobile practices are shaped by practitioners

Efficient Quantum Circuits for Non-Qubit Quantum Error-Correcting Codes

We present two methods for the construction of quantum circuits for quantum error-correcting codes (QECC). The underlying quantum systems are tensor products of subsystems (qudits) of equal dimension which is a prime power. For a QECC encoding k qudits into n qudits, the resulting quantum circuit has O(n(n-k)) gates. The running time of the classical algorithm to compute the quantum circuit is O(n(n-k)^2).Comment: 18 pages, submitted to special issue of IJFC

Why culture matters for transport policy: the case of cycling in the UK

Policy seeks to support cycling as a form of sustainable and active travel, yet, cycling levels in the UK remain low and evidence about interventions mixed. Data from a qualitative sociological study is used here to explore the difference that cultural meanings make to cycling practices in four different English urban areas. Specifically, we discuss differences between places with established cycling cultures and those with newer cycling cultures. Drawing on concepts from practice theory we discuss the role that cultures of cycling play within the four places, and suggest how the meanings of cycling, including its association with other social identities, are connected to the materials and competences seen as necessary for cycling. Our research highlights the embedding of transport in local as well as national cultures, and the associated need for policy-makers to take culture seriously in considering how to shift transport practices

On the ground states of the Bernasconi model

The ground states of the Bernasconi model are binary +1/-1 sequences of length N with low autocorrelations. We introduce the notion of perfect sequences, binary sequences with one-valued off-peak correlations of minimum amount. If they exist, they are ground states. Using results from the mathematical theory of cyclic difference sets, we specify all values of N for which perfect sequences do exist and how to construct them. For other values of N, we investigate almost perfect sequences, i.e. sequences with two-valued off-peak correlations of minimum amount. Numerical and analytical results support the conjecture that almost perfect sequences do exist for all values of N, but that they are not always ground states. We present a construction for low-energy configurations that works if N is the product of two odd primes.Comment: 12 pages, LaTeX2e; extended content, added references; submitted to J.Phys.

Simulations of diamond nucleation in carbon fullerene cores

Recent experiments have shown that heavy ion or electron irradiation induces the nucleation of diamond crystallites inside concentric nested carbon fullerenes, i.e., bucky onions. This suggests that the fullerene acts as a nanoscopic pressure shell. In this paper we study the formation of tetrahedrally bonded carbon inside a prototype icosahedral two-shell fullerene by means of atomic-scale computer simulations. After the simulated irradiation, we can identify regions in which almost all carbon atoms become sp3 bonded. Additionally, we observe a counteracting tendency for the carbon atoms to form shell-like substructures. To shift the balance between these two processes towards diamond nucleation strongly nonequilibrium conditions are required.Peer reviewe

Properties of small carbon clusters inside the C60 fullerene

We present the results of an atomic-scale simulation of the confinement of small carbon clusters inside icosahedral C60 fullerene. We carefully investigate the incorporation of various clusters into C60 including chains, rings, and double ring configurations, and have analyzed both the energetics and the resulting geometries. The calculations have been performed employing the density-functional-based tight-binding methodology within the self-consistent charge representation. We find that certain carbon cluster configurations that are unstable as free molecules become stabilized inside C60. By adding single atoms into random positions inside the fullerene shell we establish an upper limit for the filling of C60 with carbon. When the number of atoms inside the fullerene exceeds ten we observe bonding to the surrounding shell and, hence, a gradual transition of the fullerene towards an sp3 rich but locally disordered carbon system.Peer reviewe

Quantum Reed-Solomon Codes

After a brief introduction to both quantum computation and quantum error correction, we show how to construct quantum error-correcting codes based on classical BCH codes. With these codes, decoding can exploit additional information about the position of errors. This error model - the quantum erasure channel - is discussed. Finally, parameters of quantum BCH codes are provided.Comment: Summary only (2 pages), for the full version see: Proceedings Applied Algebra, Algebraic Algorithms and Error-Correcting Codes (AAECC-13), Lecture Notes in Computer Science 1719, Springer, 199

Delamination growth in buckled composite struts

Existing analytical models dealing with buckling and postbuckling phenomena of delaminated composites comprise one limitation: the restriction to stationary delaminations. In the current work, an analytical framework is presented which allows to model the postbuckling response of composites without such limitation. Therefore, the well-known problem of a composite strut with a through-the-width delamination is studied. The system is fully described by a set of I generalized coordinates. The postbuckling response for a stationary delamination is modelled using the conventional total potential energy approach. The postbuckling response for a non-stationary delamination, i.e. once delamination growth occurs, is modelled using an extended total potential energy functional in which the delamination length is expressed by the generalized coordinates and the load parameters. By solving the underlying variational principle the postbuckling response is obtained. Implementing the Rayleigh–Ritz method yields a set of non-linear algebraic equations which is solved numerically. Postbuckling responses for a cross-ply laminate are provided until the strut fails. Depending on delamination depth and length additional load bearing capacities of such composite struts are documented before failure due to unstable delamination growth occurs

Tree-based Coarsening and Partitioning of Complex Networks

Many applications produce massive complex networks whose analysis would benefit from parallel processing. Parallel algorithms, in turn, often require a suitable network partition. For solving optimization tasks such as graph partitioning on large networks, multilevel methods are preferred in practice. Yet, complex networks pose challenges to established multilevel algorithms, in particular to their coarsening phase. One way to specify a (recursive) coarsening of a graph is to rate its edges and then contract the edges as prioritized by the rating. In this paper we (i) define weights for the edges of a network that express the edges' importance for connectivity, (ii) compute a minimum weight spanning tree $T^m$ with respect to these weights, and (iii) rate the network edges based on the conductance values of $T^m$'s fundamental cuts. To this end, we also (iv) develop the first optimal linear-time algorithm to compute the conductance values of \emph{all} fundamental cuts of a given spanning tree. We integrate the new edge rating into a leading multilevel graph partitioner and equip the latter with a new greedy postprocessing for optimizing the maximum communication volume (MCV). Experiments on bipartitioning frequently used benchmark networks show that the postprocessing already reduces MCV by 11.3%. Our new edge rating further reduces MCV by 10.3% compared to the previously best rating with the postprocessing in place for both ratings. In total, with a modest increase in running time, our new approach reduces the MCV of complex network partitions by 20.4%

Pairing in Many-Fermion Systems: An Exact Renormalisation Group Treatment

We study the application of the exact renormalisation group to a many-fermion system with a short-range attractive force. We introduce a boson field to describe pairing effects, and take a simple ansatz for the effective action. We derive a set of approximate flow equations for the effective coupling including boson and fermionic fluctuations. The initial conditions are obtained by renormalising the interaction to fit the scattering length in vacuum. At some critical value of the running scale, the numerical solutions show a phase transition to a gapped phase. Standard results are recovered if we omit the boson loops. When boson fluctuations are included, we find that their contributions are significant only in the small-gap regime.Comment: 12 pages (RevTeX), 2 figures (eps