210 research outputs found
Driver reaction to navigation instructions incorporating good and poor landmarks
The study consisted of a road-based trial involving 48 participants using a navigation system to complete a
complex urban route. The participants were divided into three matched groups experiencing one of the following landmark conditions: good, poor or no landmarks, incorporated in verbal instructions. A range of objective and
subjective measures were taken to assess driver performance with and attitudes to each of the landmark
categories. The aims were to:
• assess the impact on driver performance and attitudes of presenting navigation instructions which included
good, poor or no landmarks
• validate the REGIONAL model, which was developed to predict the navigational value of individual landmarks
• identify any other factors (e.g. driver or manoeuvre characteristics) that may affect the value of landmark
Infinite N phase transitions in continuum Wilson loop operators
We define smoothed Wilson loop operators on a four dimensional lattice and
check numerically that they have a finite and nontrivial continuum limit. The
continuum operators maintain their character as unitary matrices and undergo a
phase transition at infinite N reflected by the eigenvalue distribution closing
a gap in its spectrum when the defining smooth loop is dilated from a small
size to a large one. If this large N phase transition belongs to a solvable
universality class one might be able to calculate analytically the string
tension in terms of the perturbative Lambda-parameter. This would be achieved
by matching instanton results for small loops to the relevant large-N-universal
function which, in turn, would be matched for large loops to an effective
string theory. Similarities between our findings and known analytical results
in two dimensional space-time indicate that the phase transitions we found only
affect the eigenvalue distribution, but the traces of finite powers of the
Wilson loop operators stay smooth under scaling.Comment: 31 pages, 9 figures, typos and references corrected, minor
clarifications adde
An Anisotropic Ballistic Deposition Model with Links to the Ulam Problem and the Tracy-Widom Distribution
We compute exactly the asymptotic distribution of scaled height in a
(1+1)--dimensional anisotropic ballistic deposition model by mapping it to the
Ulam problem of finding the longest nondecreasing subsequence in a random
sequence of integers. Using the known results for the Ulam problem, we show
that the scaled height in our model has the Tracy-Widom distribution appearing
in the theory of random matrices near the edges of the spectrum. Our result
supports the hypothesis that various growth models in dimensions that
belong to the Kardar-Parisi-Zhang universality class perhaps all share the same
universal Tracy-Widom distribution for the suitably scaled height variables.Comment: 5 pages Revtex, 3 .eps figures included, new references adde
Hand grip diversity and frequency during the use of Lower Palaeolithic stone cutting-tools
The suite of anatomical features contributing to the unique gripping capabilities of the modern human hand evolved alongside the proliferation of Lower Palaeolithic flaked tool technologies across the Old World. Experimental studies investigating their potential co-evolution suggest that the use of flakes, handaxes, and other stone tools is facilitated by manipulative capabilities consistent with the evolutionary trajectory of the hominin hand during this period. Grip analyses have provided important contributions to this understanding. To date, however, there has been no large-scale investigation of grip diversity during flaked stone-tool use, empirical comparative analyses of grip use frequencies, or examination of ergonomic relationships between grip choice and stone tool type and form.
Here, we conduct four experimental studies, using replica Lower Palaeolithic stone tools in a series of actualistic and laboratory-based contexts, to record grip type and frequency of grip use during 1067 stone tool-use events by 123 individuals. Using detailed morphometric data recorded from each tool, we demonstrate how grip choice varies according to the type and form of stone tool used, and how these relationships differ between tool-use contexts. We identify 29 grip types across all tool-use events, with significant differences recorded in their frequency of use dependent on tool type, tool form, and the context of use. Despite the influence of these three factors, there is consistency in the frequent use of a limited number (?4) of grip types within each experiment and the consistent and seemingly forceful recruitment of the thumb and index finger. Accordingly, we argue that there are deep-rooted, ergonomically-related, regularities in how stone tools are gripped during their use, that these regularities may have been present during the use of stone tools by Plio-Pleistocene hominins, and any subsequent selective pressures would likely have been focused on the first and second digit
Universal Critical Behavior of Aperiodic Ferromagnetic Models
We investigate the effects of geometric fluctuations, associated with
aperiodic exchange interactions, on the critical behavior of -state
ferromagnetic Potts models on generalized diamond hierarchical lattices. For
layered exchange interactions according to some two-letter substitutional
sequences, and irrelevant geometric fluctuations, the exact recursion relations
in parameter space display a non-trivial diagonal fixed point that governs the
universal critical behavior. For relevant fluctuations, this fixed point
becomes fully unstable, and we show the apperance of a two-cycle which is
associated with a novel critical behavior. We use scaling arguments to
calculate the critical exponent of the specific heat, which turns out
to be different from the value for the uniform case. We check the scaling
predictions by a direct numerical analysis of the singularity of the
thermodynamic free-energy. The agreement between scaling and direct
calculations is excellent for stronger singularities (large values of ). The
critical exponents do not depend on the strengths of the exchange interactions.Comment: 4 pages, 1 figure (included), RevTeX, submitted to Phys. Rev. E as a
Rapid Communicatio
Surface Magnetization of Aperiodic Ising Quantum Chains
We study the surface magnetization of aperiodic Ising quantum chains. Using
fermion techniques, exact results are obtained in the critical region for
quasiperiodic sequences generated through an irrational number as well as for
the automatic binary Thue-Morse sequence and its generalizations modulo p. The
surface magnetization exponent keeps its Ising value, beta_s=1/2, for all the
sequences studied. The critical amplitude of the surface magnetization depends
on the strength of the modulation and also on the starting point of the chain
along the aperiodic sequence.Comment: 11 pages, 6 eps-figures, Plain TeX, eps
Determinant representation for some transition probabilities in the TASEP with second class particles
We study the transition probabilities for the totally asymmetric simple
exclusion process (TASEP) on the infinite integer lattice with a finite, but
arbitrary number of first and second class particles. Using the Bethe ansatz we
present an explicit expression of these quantities in terms of the Bethe wave
function. In a next step it is proved rigorously that this expression can be
written in a compact determinantal form for the case where the order of the
first and second class particles does not change in time. An independent
geometrical approach provides insight into these results and enables us to
generalize the determinantal solution to the multi-class TASEP.Comment: Minor revision; journal reference adde
Educational risk factors for psychological truancy in Lesotho: a qualitative exploration
A qualitative case study design was used to explore educational risk factors that may contribute to psychological truancy in a Lesotho secondary school. Purposively sampled teachers (n = 4, females = 50%) and pupils (n = 4, females = 75%), who have experience of psychological truancy, took part in a focus group and individual interviews. Inductive content analysis was used to analyse data emanating from the interviews. The findings indicate that pupil–teacher relationships, the use of English as medium of instruction and a lack of resources may be educational risk factors contributing to psychological truancy. Positive pupil–teacher relationships and active classroom engagement are prerequisites for successful and active learning
A case-only study to identify genetic modifiers of breast cancer risk for BRCA1/BRCA2 mutation carriers
Real-time synchronization of batch trajectories for on-line multivariate statistical process control using Dynamic Time Warping
This paper addresses the real-time monitoring of batch processes with multiple different local time trajectories of variables measured during the process run. For Unfold Principal Component Analysis (U-PCA)—or Unfold Partial Least Squares (U-PLS)-based on-line monitoring of batch processes, batch runs need to be synchronized, not only to have the same time length, but also such that key events happen at the same time. An adaptation from Kassidas et al.'s approach [1] will be introduced to achieve the on-line synchronization of batch trajectories using the Dynamic Time Warping (DTW) algorithm. In the proposed adaptation, a new boundaries definition is presented for accurate on-line synchronization of an ongoing batch, together with a way to adapt mapping boundaries to batch length. A relaxed greedy strategy is introduced to avoid assessing the optimal path each time a new sample is available. The key advantages of the proposed strategy are its computational speed and accuracy for the batch process context. Data from realistic simulations of a fermentation process of the Saccharomyces cerevisae cultivation are used to illustrate the performance of the proposed strategy.This research work was supported by the Spanish government under the project (DPI2008-06880-C03-03). We also gratefully acknowledge Jose Camacho PhD. for providing simulated data from a fermentation process of Saccharomyces cerevisae. The authors would also like to acknowledge the valuable suggestions made by Prof. Paul Taylor.González MartĂnez, JM.; Ferrer Riquelme, AJ.; Westerhuis, JA. (2011). Real-time synchronization of batch trajectories for on-line multivariate statistical process control using Dynamic Time Warping. Chemometrics and Intelligent Laboratory Systems. 105(2):195-206. https://doi.org/10.1016/j.chemolab.2011.01.003S195206105
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