LHIP: Extended DCGs for Configurable Robust Parsing

We present LHIP, a system for incremental grammar development using an extended DCG formalism. The system uses a robust island-based parsing method controlled by user-defined performance thresholds.Comment: 10 pages, in Proc. Coling9

Modelling the temperature, maturity and moisture content in a drying concrete block

In this paper we continue work from a previous Study Group in developing a model for the maturation of concrete. The model requires equations describing the temperature, moisture content and maturity (or amount of cement that has reacted with the water). Non-dimensionalisation is used to simplify the model and provide simple analytical solutions which are valid for early time maturation. A numerical scheme is also developed and simulations carried out for maturation over one day and then two months. For the longer simulation we also investigate the effect of building the block in a single pour or two stages

Modelling surface heat exchanges from a concrete block to the environment

The presented problem was to determine an appropriate heat transfer boundary condition at the surface of a concrete slab exposed to the environment. The condition obtained involves solar radiation and convective heat transfer, other terms were shown to be small compared to these. It is shown that this boundary condition leads to a temperature variation that has qualitative agreement with experiments carried out by the Cement and Concrete Institute

Opening Address to the 2nd International Conference on Concrete Repair, Rehabilitation and Retrofitting. Cape Town 24 November 2008.

Opening Address to the 2nd International Conference on Concrete Repair, Rehabilitation and Retrofitting. Cape Town 24 November 2008.Most people, whether consciously or unconsciously, are attracted to what I shall call, the “great human narrative” of transformation through journey. We find the narrative attractive because it appears prominently - as a leitmotif - in much of the way in which we construct our religious and cultural understandings of ourselves. The journey narrative speaks strongly to our sense of identity - both as belonging to a group (tribe, nation, human, etc) but also as individual (adult, academic, gardener, etc). We recognise these identities as having been formed through difficult intellectual, spiritual and often, physical journey. Importantly, we think of the personal as well as the shared journey as a process towards a better understanding of complexity – towards a more enlightened view of the world and our place in it

Maturity effects in concrete dams

Model equations for determining the coupled heat, moisture and maturity changes within a concrete block are introduced and briefly examined. Preliminary results are obtained for the heat exchange between concrete slabs in contact driven by maturity differences

Modelling the cooling of concreate by piped water

Large concrete structures are usually made sequentially in a series of blocks. After each block is poured it must be left to cool and shrink for a period depending on its size, but typically for around 1 week, before the next block is poured. The reason for the delay is that the mixture of cement and water, which constitute the binding agent of the concrete, results in a series of hydration reactions that generate heat.Piped water is used to remove hydration heat from concrete blocks during construction. In this paper we develop an approximate model for this process. The problem reduces to solving a one-dimensional heat equation in the concrete, coupled with a first order differential equation for the water temperature. Numerical results are presented and the effect of varying model parameters shown. An analytical solution is also provided for a steady-state constant heat generation model. This helps highlight the dependence on certain parameters and can therefore provide an aid in the design of cooling systems

Piped water cooling of concrete dams

Piped water is used to remove hydration heat from concrete dams during construction. By examining simple models we obtain an estimate for the temperature rise along the pipe network and within the concrete. To leading order, for practically useful networks, the temperature distribution is quasi-steady, so that exact analytic solutions are obtained. The temperature in the water increases linearly with distance along the pipe and varies logarithmically with radial distance from the pipe in the concrete. Using these results we obtained estimates for the optimal spacing of pipes and pipe length. Some preliminary work on optimal network design has been done. This is work in progress

The effects of supplementary cementing materials in modifying the heat of hydration of concrete

Supplementary cementing materials, such as ground granulated blastfurnace slag(GGBS), fly ash (FA) and condensed silica fume (CSF), are now routinely used in structural concrete. Used judiciously, these materials are able to provide improvements in the economy, microstructure of cement paste as well as the engineering properties and durability of concrete. They also alter the rate of hydration and can influence the time-temperature profile in large concrete elements