Seepage and pore pressures around contiguous pile retaining walls

Diaphragm and bored pile retaining walls are often used for the construction of basements, metro station boxes and cut-and-cover tunnels in urban areas. While diaphragm and secant pile walls are generally intended (and assumed in analysis) to be effectively impermeable, contiguous piles may allow through-the-wall seepage even when preventative measures have been undertaken. Provided the flowrates can be tolerated or dealt with, through-the-wall seepage should result in a reduction in pore water pressures behind the retaining wall compared with an impermeable construction, giving the potential for reductions in the depth of embedment and wall thickness, hence cost. However, this potential is rarely realised owing to the difficulty in quantifying with sufficient confidence the hydraulic regime associated with a leaky retaining wall. This paper reports the results of laboratory investigations and numerical analyses carried out to assess the effect of the inter-pile gaps on the pore pressure distribution around a contiguous pile retaining wall. The results show that the pore pressures behind the piles reduce significantly as the pile spacing is increased. Long-term field monitoring confirms that the pore water pressures are much lower than would be expected for an impermeable retaining wall in similar soil. The applicability of a simple expression linking the pile diameter, pile spacing and the effective permeability of an equivalent uniform wall is demonstrated

Affordable High Powered Clustered Computing for Aerospace Simulation. G.U. Aero Report 9911

Motivated by a lack of sufficient local and national computing facilities for computational fluid dynamics simulations, the Affordable Systems Computing Unit (ASCU) was established to investigate low cost alternatives. The options considered have all involved cluster computing, a term which refers to the grouping of a number of components into a managed system capable of running both serial and parallel applications. Past work by the Unit has demonstrated the significant improvement in the efficiency of a Network of Workstations when management software is employed to scavenge spare cycles and schedule tasks, and has also investigated the use of a managed network for parallel CFD. The present work aims to extend this effort to a higher performance cluster based on commodity processors used for dedicated batch processing. The performance of the cluster has proved to be extremely cost effective, producing a 3 Gigaflops plus peak performance for less than 25K U.K. pounds sterling at current market prices. The experience gained on this system in terms of single node performance, message passing and parallel performance will be discussed. In particular, comparisons with the performance of other systems will be made. A large scale CFD simulation achieved using the new cluster will be presented to demonstrate the potential of commodity processor based parallel computers for aerodynamic simulation

Computation of protein geometry and its applications: Packing and function prediction

This chapter discusses geometric models of biomolecules and geometric constructs, including the union of ball model, the weigthed Voronoi diagram, the weighted Delaunay triangulation, and the alpha shapes. These geometric constructs enable fast and analytical computaton of shapes of biomoleculres (including features such as voids and pockets) and metric properties (such as area and volume). The algorithms of Delaunay triangulation, computation of voids and pockets, as well volume/area computation are also described. In addition, applications in packing analysis of protein structures and protein function prediction are also discussed.Comment: 32 pages, 9 figure

A Fragmented Parallel Stream: The Bass Lines of Eddie Gomez in the Bill Evans Trio

Eddie Gomez was the bassist in the Bill Evans Trio for eleven years. His contribution to the group’s sound was considerable, but while there has been some recognition of his virtuoso solos in the trio there has been little academic interest in his bass lines. This essay examines bass lines from the album Since We Met, recorded in 1974 by Evans, Gomez and drummer Marty Morell. Analysis of the bass accompaniments to the piano solos on “Since We Met” and “Time Remembered” reveals that they form a fragmented two-feel. A traditional two-feel employs two notes to emphasise the first and third beats in bar of 4/4 time. In Gomez’s bass lines these two notes are frequently replaced with short rhythmic motifs. These motifs occur in a variety of forms and at different metric displacements that alternately propel and retard the forward motion of the music. Additionally, Gomez uses a wide range of register and varied articulations to create a richly diverse bass line. The resulting effect has often been interpreted as interactive or conversational with the soloist. However there is very little interaction between the bass line and Evans’ solo. The bass line is a parallel stream to the solo that energises and colours the music

Current Fluctuations of the One Dimensional Symmetric Simple Exclusion Process with Step Initial Condition

For the symmetric simple exclusion process on an infinite line, we calculate exactly the fluctuations of the integrated current $Q_t$ during time $t$ through the origin when, in the initial condition, the sites are occupied with density $\rho_a$ on the negative axis and with density $\rho_b$ on the positive axis. All the cumulants of $Q_t$ grow like $\sqrt{t}$. In the range where $Q_t \sim \sqrt{t}$, the decay $\exp [-Q_t^3/t]$ of the distribution of $Q_t$ is non-Gaussian. Our results are obtained using the Bethe ansatz and several identities recently derived by Tracy and Widom for exclusion processes on the infinite line.Comment: 2 figure

Deep Radio Continuum Studies with the SKA: Evolution of Radio AGN Populations

Radio emission is insensitive to dust obscuration, and the breadth of the radio luminosity function ensures that sources are detected over a wide range of redshifts at all radio flux densities. As a result, radio continuum observations are an efficient and unbiased probe of both nuclear (AGN) and star-forming activity over all cosmic epochs. The SKA's ``ultra-deep radio continuum surveys'' will provide the answers to at least three key astrophysical questions: (i) the star-formation history of the Universe, (ii) the evolution of the low-power end of the radio galaxy luminosity function and (iii) the relationship between the radio-loud AGN, star-formation and radio-quiet AGN phenomena. In this paper we discuss the AGN science that will be enabled by the deep radio continuum studies using the SKA. It is important to recognise that the sub-microJy SKA sky will be dominated by populations other than `radio-loud' AGN. In this way the SKA will not only provide an unbiased tracer of the star-formation history of the Universe but also be able to study the populations of sources we currently describe as `radio-quiet'. To illustrate this point we present simulations of the extragalactic radio sky based from models of the evolution of the radio luminosity function. From these simulations we predict typical source distributions and estimate the natural confusion limit to ultra-faint flux density limits relevant to the science and design goals of the SKA.Comment: 8 pages, 2 figures (b/w only, full colour available at http://www.atnf.csiro.au/~cjackson . To to appear in "Science with the Square Kilometre Array" eds. C. Carilli and S. Rawlings, New Astronomy Reviews (Elsevier: Amsterdam

Near-field optical power transmission of dipole nano-antennas

Nano-antennas in functional plasmonic applications require high near-field optical power transmission. In this study, a model is developed to compute the near-field optical power transmission in the vicinity of a nano-antenna. To increase the near-field optical power transmission from a nano-antenna, a tightly focused beam of light is utilized to illuminate a metallic nano-antenna. The modeling and simulation of these structures is performed using 3-D finite element method based full-wave solutions of Maxwell’s equations. Using the optical power transmission model, the interaction of a focused beam of light with plasmonic nanoantennas is investigated. In addition, the tightly focused beam of light is passed through a band-pass filter to identify the effect of various regions of the angular spectrum to the near-field radiation of a dipole nano-antenna. An extensive parametric study is performed to quantify the effects of various parameters on the transmission efficiency of dipole nano-antennas, including length, thickness, width, and the composition of the antenna, as well as the wavelength and half-beam angle of incident light. An optimal dipole nanoantenna geometry is identified based on the parameter studies in this work. In addition, the results of this study show the interaction of the optimized dipole nano-antenna with a magnetic recording medium when it is illuminated with a focused beam of light

The Simple View of Reading Made Complex by Morphological Decoding Fluency in Bilingual Fourth-Grade Readers of English

This is the author accepted manuscript. The final version is available from Wiley via the DOI in this recordThis study examined the complexity of the Simple View of Reading focusing on morphological decoding fluency in fourth-grade readers of English in Singapore. The participants were three groups of students who all learned to become bilingual and biliterate in the English language (EL) and their respective ethnic language in school but differed in the home language they used. The first group was ethnic Chinese students who used English as the dominant home language (Chinese EL1); the other two groups were ethnic Chinese and Malay students whose dominant home language was not English but Chinese (Chinese EL2) and Malay (Malay EL2), respectively. The measures included pseudo word decoding (phonemic decoding), timed decoding of derivational words (morphological decoding fluency), oral vocabulary, and passage comprehension. Path analysis showed that oral vocabulary significantly predicted reading comprehension across all three groups; yet a significant effect of morphological decoding fluency surfaced in the Chinese EL1 and Malay EL2 groups but not the Chinese EL2 group. Multi-group path analysis and commonality analysis further confirmed that morphological decoding played a larger role in the in the Chinese EL1 and Malay EL2 groups. These findings are discussed in light of the joint influence of target language experience and cross-linguistic influence on second language or bilingual reading development.Office of Education Research, National Institute of Education, Nanyang Technological Universit

Telecommunication wavelength GaAsBi light emitting diodes

GaAsBi light emitting diodes containing ∼6% Bi are grown on GaAs substrates. Good room-temperature electroluminescence spectra are obtained at current densities as low as 8 Acm − 2. Measurements of the integrated emitted luminescence suggest that there is a continuum of localised Bi states extending up to 75 meV into the bandgap, which is in good agreement with previous photoluminescence studies. X-ray diffraction analysis shows that strain relaxation has probably occurred in the thicker samples grown in this study

Quasars and their host galaxies

This review attempts to describe developments in the fields of quasar and quasar host galaxies in the past five. In this time period, the Sloan and 2dF quasar surveys have added several tens of thousands of quasars, with Sloan quasars being found to z>6. Obscured, or partially obscured quasars have begun to be found in significant numbers. Black hole mass estimates for quasars, and our confidence in them, have improved significantly, allowing a start on relating quasar properties such as radio jet power to fundamental parameters of the quasar such as black hole mass and accretion rate. Quasar host galaxy studies have allowed us to find and characterize the host galaxies of quasars to z>2. Despite these developments, many questions remain unresolved, in particular the origin of the close relationship between black hole mass and galaxy bulge mass/velocity dispersion seen in local galaxies.Comment: Review article, to appear in Astrophysics Update