6,923 research outputs found
The BDSIM Toolkit
This report is a description of the BDSIM toolkit based on the User's Manual for the v0.1 version
BDSIM-Beamline Simulation Toolkit Based on GEANT4
http://cern.ch/AccelConf/e06/PAPERS/WEPCH124.PDFInternational audienceBDSIM is a code that combines accelerator-style par- ticle tracking with traditional Geant-style tracking based on Runge-Kutta techniques. This approach means that particle beams can be tracked efïŹciently when inside the beampipe, while also enabling full Geant4 processes when beam-particles interact with beamline apertures. Tracking of the resulting secondary particles is automatic. The code is described, including a new MAD-style interface and new geometry description, and key performance parameters are listed
Vortex pairing in two-dimensional Bose gases
Recent experiments on ultracold Bose gases in two dimensions have provided
evidence for the existence of the Berezinskii-Kosterlitz-Thouless (BKT) phase
via analysis of the interference between two independent systems. In this work
we study the two-dimensional quantum degenerate Bose gas at finite temperature
using the projected Gross-Pitaevskii equation classical field method. While
this describes the highly occupied modes of the gas below a momentum cutoff, we
have developed a method to incorporate the higher momentum states in our model.
We concentrate on finite-sized homogeneous systems in order to simplify the
analysis of the vortex pairing. We determine the dependence of the condensate
fraction on temperature and compare this to the calculated superfluid fraction.
By measuring the first order correlation function we determine the boundary of
the Bose-Einstein condensate and BKT phases, and find it is consistent with the
superfluid fraction decreasing to zero. We reveal the characteristic unbinding
of vortex pairs above the BKT transition via a coarse-graining procedure.
Finally, we model the procedure used in experiments to infer system
correlations [Hadzibabic et al., Nature 441, 1118 (2006)], and quantify its
level of agreement with directly calculated in situ correlation functions.Comment: published versio
Specification and Verification of Media Constraints using UPPAAL
We present the formal specification and verification of a multimedia stream. The stream is described in a timed automata notation. We verify that the stream satisfies certain quality of service properties, in particular, throughput and end-to-end latency. The verification tool used is the real-time model checker UPPAAL
Late-time oscillatory behaviour for self-gravitating scalar fields
This paper investigates the late-time behaviour of certain cosmological
models where oscillations play an essential role. Rigorous results are proved
on the asymptotics of homogeneous and isotropic spacetimes with a linear
massive scalar field as source. Various generalizations are obtained for
nonlinear massive scalar fields, -essence models and gravity. The
effect of adding ordinary matter is discussed as is the case of nonlinear
scalar fields whose potential has a degenerate zero.Comment: 17 pages, additional reference
Comparison and relative utility of inequality measurements: as applied to Scotlandâs child dental health
This study compared and assessed the utility of tests of inequality on a series of very large population caries datasets. National cross-sectional caries datasets for Scotlandâs 5-year-olds in 1993/94 (n = 5,078); 1995/96 (n = 6,240); 1997/98 (n = 6,584); 1999/00 (n = 6,781); 2002/03 (n = 9,747); 2003/04 (n = 10,956); 2005/06 (n = 10,945) and 2007/08 (n = 12,067) were obtained. Outcomes were based on the d3mft metric (i.e. the number of decayed, missing and filled teeth). An area-based deprivation category (DepCat) measured the subjectsâ socioeconomic status (SES). Simple absolute and relative inequality, Odds Ratios and the Significant Caries Index (SIC) as advocated by the World Health Organization were calculated. The measures of complex inequality applied to data were: the Slope Index of Inequality (absolute) and a variety of relative inequality tests i.e. Gini coefficient; Relative Index of Inequality; concentration curve; Koolman and Doorslaerâs transformed Concentration Index; Receiver Operator Curve and Population Attributable Risk (PAR). Additional tests used were plots of SIC deciles (SIC10) and a Scottish Caries Inequality Metric (SCIM10). Over the period, mean d3mft improved from 3.1(95%CI 3.0â3.2) to 1.9(95%CI 1.8â1.9) and d3mft = 0% from 41.1(95%CI 39.8â42.3) to 58.3(95%CI 57.8â59.7). Absolute simple and complex inequality decreased. Relative simple and complex inequality remained comparatively stable. Our results support the use of the SII and RII to measure complex absolute and relative SES inequalities alongside additional tests of complex relative inequality such as PAR and Koolman and Doorslaerâs transformed CI. The latter two have clear interpretations which may influence policy makers. Specialised dental metrics (i.e. SIC, SIC10 and SCIM10) permit the exploration of other important inequalities not determined by SES, and could be applied to many other types of disease where ranking of morbidity is possible e.g. obesity. More generally, the approaches described may be applied to study patterns of health inequality affecting worldwide populations
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