213 research outputs found
A bifurcated circular waveguide problem
No full textThis is a pre-copy-editing, author-produced PDF of an article accepted for publication in IMA Journal of Applied Mathematics following peer review. The definitive publisher-authenticated version A D Rawlins. A bifurcated circular waveguide problem. J.I.M.A. 54 (1995) 59-81. Oxford University press is available online at: http://imamat.oxfordjournals.org/cgi/reprint/54/1/59.pdfA rigorous and exact solution is obtained for the problem of the radiation of sound from a semi-infinite rigid duct inserted axially into a larger acoustically lined tube of infinite length. The solution to this problem is obtained by the Wiener-Hopf technique. The transmission and reflection coefficients, when the fundamental mode propagates in the semi-infinite tube, are obtained. The present results could be of use for exhaust design, and as a possible instrument for impedance measurement
A note on Wiener-Hopf matrix factorisation
No full textThis is a pre-copy-editing, author-produced PDF of an article accepted for publication in Quarterly Journal of Mechanics and Applied Mathematics following peer review. The definitive publisher-authenticated version Rawlins, A D (1985). A note on Wiener-Hopf matrix factorisation. Quarterly Journal of Mechanics and Applied Mathematics. 38 (3) 433-437 is available online at: http://qjmam.oxfordjournals.org/cgi/reprint/38/3/433.pdfIn this paper the most general class of 2 x 2 matrices is determined which permit a
Wiener-Hopf factorization by the procedure of Rawlins and Williams (1). According
to this procedure, the factorization problem is reduced to a matrix Hilbert problem
on a half-line, where the matrix involved in the Hilbert problem is required to have
zero diagonal elements
Can a paleosol be used as a reference material for monitoring soil aggregate stability?
No full textAn important physical indicator of soil quality, which regulatory authorities may wish to monitor, is aggregate
stability. In a recent study, Rawlins et al. (in press) presented a novel method for determining the stability of aggregates
in water using a laser granulometer (LG). The LG is used to make two measurements of the continuous
size distribution (<2000 μm) within a sample of aggregates. The first measurement is made on water stable aggregates
after these have been added to circulating water (initial air-dried aggregate size range 1000 to 2000 μm). The
second measurement is made on the disaggregated material after the circulating aggregates have been disrupted
with ultrasound (sonication). The difference between the mean weight diameters of these two size distributions
is referred to as the disaggregation reduction (DR; μm). Soils with more stable aggregates, which are resistant
to both slaking and mechanical breakdown by the hydrodynamic forces during circulation, have larger values of
DR. Rawlins et al showed that for two soil types, the DR values had coefficients of variation of 12.1 and 19%
suggesting the DR value is reproducible based on the small mass of soil used. If such a test is to be applied for
soil aggregate monitoring, it will be necessary to analyse a reference material (RM) with consistent disaggregation
properties (DR value) to demonstrate that the procedure is consistent over the period of monitoring.
To our knowledge no one has previously attempted to use or apply a RM for testing soil aggregate stability.
We know of no commercially available anthropogenic material which has consistent disaggregation properties.
Field soils, which are exposed to seasonal variations in organic matter content plus wetting and drying cycles, are
unlikely to have sufficiently consistent disaggregation properties for use as an aggregate RM. Paleosols are likely
to be less reposnosive to seasoanl cycles because they are often buried at depths (>1 m) beyond the most active
hydrological and biogeochemical cycles, and so they are likely to disaggregate more consistently over time. They
are also sufficiently abundant for bulk samples to be collected repeatedly.We present analyses of DR for a paleosol
(brickearth) material collected from a site at Ospringe in Kent (sourthern England) at a depth of 1.6 m to determine
whether it has properties that indicate its potential for use as a RM for monitoring soil aggregate stability based on
the method presented by Rawlins et al.. We discuss the implications of our initial findings.
Rawlins, B. G., Wragg, J. Lark, R. M. in press. Application of a novel method for soil aggregate stability measurement
by laser granulometry with sonication. European Journal of Soil Science
The method of finite-product extraction and an application to Wiener-Hopf theory
No full textCopyright @ The Author, 2011. The publisher version of the article can be accessed at the link below.In this work we describe a simple method for finding approximate representations for special functions which are entire transcendental functions that can be represented by infinite products. This method replaces the infinite product by a finite polynomial and Gamma functions. This approximate representation is shown in the case of Bessel functions to be very accurate over a large range of parameter values. These approximate expressions can be useful for finding the roots of a transcendental equation and the Wiener-Hopf factorization of functions involving such Bessel functions.The method is shown to be potentially useful for other transcendental andWiener-Hopf problems, which involve other entire functions that have infinite product representations
Comment on : 'multi-element signatures of stream sediments and sources under moderate to low flow conditions' by M.I. Stutter, S.J. Langan, D.G. Lumsdon, L.M. Clark
No full textIn a recent paper on ‘Multi-element signatures of stream sediments and sources under moderate to low flow conditions’, Stutter et al., 2009 M.I. Stutter, S.J. Langan, D.G. Lumsdon and L.M. Clark, Multi-element signatures of stream sediments and sources under moderate to low flow conditions, Appl. Geochem. 24 (2009), pp. 800–809. Article | PDF (392 K) | View Record in Scopus | Cited By in Scopus (2)Stutter et al. (2009) presented results of a simple sediment source tracing method based on major and trace elements for a small agricultural catchment in NE Scotland. The authors reported statistically significant, larger concentrations of four trace elements (Ce, Nd, Th and Y) in bank subsoils (n = 5) and stream bed sediments (n = 3) compared to topsoils from both pasture (n = 5) and arable (n = 5) land. They used these differences to aid discrimination between topsoil and subsoil (stream bank erosion) contributions to bed sediment. These elements may be more depleted in topsoil compared to subsoil because the former have been subject to more intense weathering over a longer period. If these naturally occurring trace elements could be used to understand the relative proportions of topsoil and subsoil contributions to headwater bed sediments this approach might be applied more widely to elucidate transport pathways for the transfer of agricultural contaminants such as particulate phosphorus to streams (Walling et al., 2008). This approach warrants further investigation across a range of catchments at different scales with contrasting land use and bedrock types. This can be undertaken using data from regional-scale geochemical surveys (Johnson et al., 2005) which include analyses of both stream bed sediments and subsoil samples. Previous studies have shown that much of lowland central England is at risk of topsoil transfer to watercourses via land drains (Chapman et al., 2003). A geochemical survey across part of central England covering 15 400 km2 was recently undertaken and these data are well-suited to testing whether three of the four trace elements identified by Stutter et al. (2009) might be used to discriminate between topsoil and subsoil in sediments more widely. Specifically, if the concentrations of these elements are significantly smaller in stream bed sediments than in the subsoil, this may be due to mixing with topsoils which have lower concentrations of these elements. Below the regional-scale survey, the methods the author used to compare the geochemical data in subsoil and bed sediments described, and the findings and their implications discussed
Tailwind Spring 1986
No full textSouthern Utah State College. Tailwind. Spring 1986. Editor. Lynn Kay Nolan. Associate Editors. John Rex. Eulail Pickering. Assistant Editors. Kelly Van Hooser. Larry Schmidt. Graphic Design. Gavin McNeil. Faculty Adviser. Sarah Solberg. Table of Contents. "Still Life," Eulail Pickering. "Poor Old Dreamer," Marie Southwell. "The Sea," Cyndy Leyson. "Sustenance," Blanche Clegg. "Idaho Dirt," Gay Harper. "In February," Nani Lii Furse. "Tropical Rain," John Rex. "Love of Learning," Brent E. Drew. "Night," Eulail Pickering. "Morning Cirrus," Leon Chidester. "Mark's Poem," Marie Southwell. "Children in the Woods," Barry Lopez. "Haiku," Rosanne Harvey. "Penitent," Leon Chidester. "Youth Without a War," Brent E. Drew. "Reflections on a Photo Never Taken in 1979," Doug Christensen. "If At First," Sheri L. Throop. "Her Love Poem #3," John Rex. "Big Cedar Dreams," G. Barnes. "Learning the Songs," Marie Southwell. "Two Days In This Place," Larry Schmidt. "Night Lake," Nani Lii Furse. "Rowing Against the Wind, Against the Tide," Samuel Green. "Belly of the Mouse," Kenneth W. Brewer. "Sacrament," C.L. Rawlins
Health Hazard Evaluation Report: HETA-81-021-850: Pacific Power and Light Company; Rawlins, Wyoming
No full textEnvironmental and personal air samples were analyzed for the presence of 1,1,1-trichloroethane (71556) at the Pacific Power and Light Company (SIC-4911) in Rawlins, Wyoming on January 27, 1981. A representative of the Utility Workers Union of America, AFL-CIO, Local 127, requested the evaluation on behalf of an unspecified number of workers. Concentrations of 1,1,1-trichloroethane in environmental and personal samples ranged from 4 to 610 milligrams per cubic meter (mg/m3), compared with the OSHA standard of 1900mg/m3 for an 8 hour time weighted average exposure. The author concludes that a 1,1,1-trichloroethane exposure hazard did not exist at the time of the survey. He recommends that an environmental study be undertaken at this facility during the summer when larger quantities of 1,1,1-trichloroethane are used, a worker education program on 1,1,1-trichloroethane hazards be implemented, and appropriate personal hygiene practices be used
Controls on the phosphorus content of fine stream bed sediments in agricultural headwater catchments at the landscape-scale
No full textThere have been no landscape-scale assessments which quantify the relative importance of the organic and mineral properties of BS (bed sediment) and associated catchment characteristics (geology, land cover and mean topsoil phosphorus (P) content) for BSP concentration. Mid infra red diffuse reflectance spectrometry was applied to estimate the quantities of organic matter, dithionite extractable aluminium- (Ald) and iron (Fed), kaolinite, dioctahedral clay and mica (D&M) minerals in 1052 snapshot samples of fine (<150 μm) BS in small to medium-sized (5–55 km2) agricultural headwater catchments across a large area (15 400 km2) of central England. Analyses included estimates of BS specific surface area, cerium (Ce) concentrations (enriched in P-bearing apatite and P-fertilsers), and catchment average topsoil P content.
Simple linear regression demonstrated that the proportion of variance in BSP explained by specific components of BS across all catchments declined in the following order: Ald > Fed > topsoil P = kaolinite = residual iron> organic matter = Ce> D&M > mineral SSA. No single component accounted for more than 36% of the variance in BSP. Multiple regression – including a classification of bedrock lithology and proportions of arable and grassland by area – accounted for 61.9% of the variance in BSP. The proportion of arable and grassland by area in each catchment was also a statistically significant predictor of BSP. Across this large region – with widely differing geology and soils – Fed in BS is more strongly associated with kaolinite than D&M minerals because iron-oxyhydroxides and kaolinite form contemporaneously during pedogenesis. The SSA of fine bed sediments is largely determined by catchment area, fitted accurately using a power function
The causes and the effects of the deficiency in the Pre-Legislative and Legislative scrutiny processes in St. Lucia
No full textThis dissertation argues that there is a significant deficiency in the pre-legislative and legislative scrutiny processes in St. Lucia, caused by the failure of Parliament to utilize the Standing Orders in the manner in which they were intended and develop and follow a more systematic scrutiny process. The author explains how this has hindered St. Lucia’s ability to gain more benefit from the legislative process and improve the quality of legislation produced with less likelihood of amendments
- …
