8,982 research outputs found
Validation of Computational Models of Auxiliary Ventilation Systems with Experimental Data
This paper reports the interim findings of a research program whose objective is to determine whether Computational Fluid Dynamic (CFD) models can be employed to accurately predict the airflow patterns within rapid development headings. In particular, the project aims to investigate the optimum set back distances for the ducts in order to adequately ventilate the face of the drivage. To validate the accuracy of the CFD model simulations measurements were obtained from a series of experiments performed on both scale models and within a full-scale surface gallery. The experimental scale-modeling program included making a series of pressure measurements across the face of the model for equivalent forcing duct setback distances of 5, 10 and 15 m (16, 33 and 50 ft). This pressure data was then plotted as contour plots and compared with the corresponding CFD predictions. A series of full-scale auxiliary ventilation trials were performed within a modified surface gallery. Three-dimensional velocity measurements were taken across a number of cross-sections using an ultrasonic anemometer. Velocity measurements were obtained for three forcing duct setback distances and for a typical force-exhaust overlap configuration
W-Extended Fusion Algebra of Critical Percolation
Two-dimensional critical percolation is the member LM(2,3) of the infinite
series of Yang-Baxter integrable logarithmic minimal models LM(p,p'). We
consider the continuum scaling limit of this lattice model as a `rational'
logarithmic conformal field theory with extended W=W_{2,3} symmetry and use a
lattice approach on a strip to study the fundamental fusion rules in this
extended picture. We find that the representation content of the ensuing closed
fusion algebra contains 26 W-indecomposable representations with 8 rank-1
representations, 14 rank-2 representations and 4 rank-3 representations. We
identify these representations with suitable limits of Yang-Baxter integrable
boundary conditions on the lattice and obtain their associated W-extended
characters. The latter decompose as finite non-negative sums of W-irreducible
characters of which 13 are required. Implementation of fusion on the lattice
allows us to read off the fusion rules governing the fusion algebra of the 26
representations and to construct an explicit Cayley table. The closure of these
representations among themselves under fusion is remarkable confirmation of the
proposed extended symmetry.Comment: 30 page
A Merger Scenario for the Dynamics of Abell 665
We present new redshift measurements for 55 galaxies in the vicinity of the
rich galaxy cluster Abell 665. When combined with results from the literature,
we have good velocity measurements for a sample of 77 confirmed cluster members
from which we derive the cluster's redshift z=0.1829 +/- 0.0005 and
line-of-sight velocity dispersion of 1390 +/- 120 km/s. Our analysis of the
kinematical and spatial data for the subset of galaxies located within the
central 750 kpc reveals only subtle evidence for substructure and
non-Gaussianity in the velocity distribution. We find that the brightest
cluster member is not moving significantly relative to the other galaxies near
the center of the cluster. On the other hand, our deep ROSAT high resolution
image of A665 shows strong evidence for isophotal twisting and centroid
variation, thereby confirming previous suggestions of significant substructure
in the hot X-ray--emitting intracluster gas. In light of this evident
substructure, we have compared the optical velocity data with N-body
simulations of head-on cluster mergers. We find that a merger of two similar
mass subclusters (mass ratios of 1:1 or 1:2) seen close to the time of
core-crossing produces velocity distributions that are consistent with that
observed.Comment: 30 pages and 7 figures. Accepted by the Astrophysical Journal Full
resoultion figures 1 and 3 available in postscript at
http://www.physics.rutgers.edu/~percy/A665paper.htm
Off-Critical Logarithmic Minimal Models
We consider the integrable minimal models , corresponding
to the perturbation off-criticality, in the {\it logarithmic
limit\,} , where are coprime and the
limit is taken through coprime values of . We view these off-critical
minimal models as the continuum scaling limit of the
Forrester-Baxter Restricted Solid-On-Solid (RSOS) models on the square lattice.
Applying Corner Transfer Matrices to the Forrester-Baxter RSOS models in Regime
III, we argue that taking first the thermodynamic limit and second the {\it
logarithmic limit\,} yields off-critical logarithmic minimal models corresponding to the perturbation of the critical
logarithmic minimal models . Specifically, in accord with the
Kyoto correspondence principle, we show that the logarithmic limit of the
one-dimensional configurational sums yields finitized quasi-rational characters
of the Kac representations of the critical logarithmic minimal models . We also calculate the logarithmic limit of certain off-critical
observables related to One Point Functions and show that the
associated critical exponents
produce all conformal dimensions in the infinitely extended Kac table. The corresponding Kac labels
satisfy . The exponent is obtained from the logarithmic limit of the free energy giving the
conformal dimension for the perturbing field . As befits a non-unitary
theory, some observables diverge at criticality.Comment: 18 pages, 5 figures; version 3 contains amplifications and minor
typographical correction
Excited Boundary TBA in the Tricritical Ising Model
By considering the continuum scaling limit of the RSOS lattice model
of Andrews-Baxter-Forrester with integrable boundaries, we derive excited state
TBA equations describing the boundary flows of the tricritical Ising model.
Fixing the bulk weights to their critical values, the integrable boundary
weights admit a parameter which plays the role of the perturbing
boundary field and induces the renormalization group flow between
boundary fixed points. The boundary TBA equations determining the RG flows are
derived in the example. The
induced map between distinct Virasoro characters of the theory are specified in
terms of distribution of zeros of the double row transfer matrix.Comment: Latex, 14 pages - Talk given at the Landau meeting "CFT and
Integrable Models", Sept. 2002 - v2: some statements about
perturbations correcte
Monitoring health inequalities: life expectancy and small area deprivation in New Zealand
BACKGROUND: Socioeconomic and ethnic inequalities in health are of great concern, and life expectancy provides a readily understood means of monitoring such inequalities. The objectives of this study are to (1) measure life expectancy by socioeconomic deprivation and ethnicity, and (2) describe trends in the deprivation gradient in life expectancy since the mid-1990s. METHODS: Three years of national mortality data have been combined with mid-point population denominators to produce life tables within nationally determined levels of small area deprivation (NZDep96) for three ethnic group: European, MĂ€ori and Pacific peoples. This process has been repeated for the periods 1995â97, 1996â98, 1997â99 and 1998â2000. RESULTS: There was a strong relationship between increasing small area deprivation and decreasing life expectancy. Through the mid- to late 1990s, males living in the most deprived small areas in New Zealand experienced life expectancies at birth approximately nine years less than their counterparts living in the least deprived areas; for females the corresponding difference was under seven years. MĂ€ori and Pacific life expectancies at birth were lower than those of Europeans at each level of deprivation. Over the study period (1995â2000) the gradient in life expectancy across deprivation deciles remained stable. CONCLUSION: Small area deprivation analyses of life expectancy could be repeated routinely at regular intervals, which would provide a useful approach to monitoring trends in socioeconomic, geographic, ethnic and gender inequalities in mortality
Peel and peel again
Aim: To determine if the internal limiting membrane (ILM) was present in the epiretinal membrane (ERM) when we deliberately tried to perform a "double peel" for macular pucker. Methods: Pars-plana vitrectomy and a "double peel" were carried out. The ERM and ILM were stained with Trypan Blue and peeled separately over the same area. The amount of ERM present in ILM specimens and the amount of ILM present in ERM specimens were evaluated by histological examination. Results: Seventeen eyes in 17 patients were included. It was possible to double peel in all cases. Five of 17 ERM specimens (29%) contained ILM fragments. When ILM was present on the ERM, it represented less than 50% of the sample. One ILM specimen was lost as result of an administrative error; of the remaining 16 specimens, residual ERM was found in six, and cellular remnants were observed on the vitreous surface in a further six of the ILMs. Clinically, no recurrence of ERM was found. Conclusion: ILM was present in some ERM specimens seemingly over the same area that an intact ILM was subsequently peel. We speculate that the ILM in the ERM represent a secondary basement membrane and that the surgical plane of dissection for most ERM peel is between the ERM and the native ILM, making it feasible to double peel routinely.published_or_final_versio
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Carbon isotope stratigraphy and palynology of an eastern Tethyan Cretaceous-Paleogene boundary section from Sumbar, Turkmenistan
A number of marine sequences across the K/Pg boundary have been identified that offer reasonably continuous records and relatively high sedimentation rates, most notably those near Tethyan continental margins. However, few Eastern Tethys K/Pg localities have been studied compared to the well-known North African and Southern European sites. Here we present a high-resolution stable carbon isotope and palynological record of a 2m thick section across the K/Pg boundary from the eastern Tethys at Sumbar in Turkmenistan (38°28âN, 56°14âE). The stratigraphy and inorganic geochemistry of the section used in this study, SM-4, has been described in detail by [1]
Introducing willingness-to-pay for noise changes into transport appraisal: an application of benefit transfer.
Numerous research studies have elicited willingness-to-pay values for transport-related noise, however, in many industrialised countries including the UK, noise costs and benefits are still not incorporated into appraisals for most transport projects and policy changes (Odgaard et al, 2005; Grant-Muller et al, 2001). This paper describes the actions recently taken in the UK to address this issue, comprising: primary research based on the city of Birmingham; an international review of willingness-to-pay evidence; development of values using benefit transfers over time and locations; and integration with appraisal methods. Amongst the main findings are: that the willingness-to-pay estimates derived for the UK are broadly comparable with those used in appraisal elsewhere in Europe; that there is a case for a lower threshold at
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45dB(A)Leq,18hr1 rather than the more conventional 55dB(A); and that values per dB(A) increase with the noise level above this threshold. There are significant issues over the valuation of rail versus road noise, the neglect of non-residential noise and the valuation of high noise levels in different countries. Conclusions are drawn regarding the feasibility of noise valuation based on benefit transfers in the UK and elsewhere, and future research needs in this field are discussed
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