A Study of kk-dipath Colourings of Oriented Graphs

We examine $t$-colourings of oriented graphs in which, for a fixed integer $k \geq 1$, vertices joined by a directed path of length at most $k$ must be assigned different colours. A homomorphism model that extends the ideas of Sherk for the case $k=2$ is described. Dichotomy theorems for the complexity of the problem of deciding, for fixed $k$ and $t$, whether there exists such a $t$-colouring are proved.Comment: 14 page

Role of Quantum Coherence and Energetic Disorder on Exciton Transport in Polymer Films

The cross-over from coherent to incoherent exciton transport in disordered polymer films is studied by computationally solving a modified form of the Redfield equation for the exciton density matrix. This theory models quantum mechanical (ballistic) and incoherent (diffusive) transport as limiting cases. It also reproduces Forster transport for certain parameter regimes. Using model parameters appropriate to polymer thin films it is shown that short-time quantum mechanical coherence increases the exciton diffusion length. It also causes rapid initial energy relaxation and larger line widths. The route to equilibrium is, however, more questionable, as the equilibrium populations of the model do not satisfy the Boltzmann distributions over the site energies. The Redfield equation for the dimer is solved exactly to provide insight into the numerical results.Comment: Accepted for publication in Phys. Rev. B. (July 2006). 19 pages and 8 figure

A water vision for Johnstone

The Water Vision is based on ideas from The Netherlands which promote communication with the public on key water related issues in a local authority area. A Water Vision for Johnstone was developed in Renfrewshire, Scotland where serious flooding has occurred in the past and new, predominantly non-structural approaches to surface water management were demanded. The paper outlines the development of a ‘Water Vision for Johnstone’ which became a key outcome of the Interreg III B project ‘Urban Water’.The Water Toets (Assessments) are statutory procedures in the Netherlands which come into play from the concept stage of developments onwards to full implementation. They are undertaken jointly on behalf of the spatial planning authority and the water authorities to evaluate the impact of development on the water network. In contrast, the Water Vision is a less well-defined process to identify community needs and aspirations but in many areas the vision is essential to support the Water Toets. The Water Vision is initiated by planning officers from the municipalities asking very basic questions of their communities about what they required of the water network. It was felt that adopting such a proactive approach where virtually any question about water bodies and drainage infrastructure could be asked, would not be practicable in the UK and it was decided to assemble information about water issues in the area, the agencies involved and potential ways forward, before approaching the public.Johnstone was selected as a test area as it was felt that this locality included many of the water related problems that can be found throughout Renfrewshire. Key water issues were identified and a range of possible solutions provided. Problems, solutions and organisations responsible for different aspects of the water network are described in the document, using images and plans to facilitate the public awareness. Normally the man in the street would not be expected to be as familiar with the nature of water-related problems as the general public in the Netherlands. The Water Vision is yet to go to public consultation as it is currently primarily a planning tool in which council processes are embedded. However, it is planned that workshops including all key stakeholders involved in water management will be held. Those bodies currently responsible for water management will then be encouraged to discuss the various options and opportunities available in a creative and integrated manner. By working together as a team in addressing water related issues it will be possible to develop a vision for the future that better assists the public in moving forward together

SUDS treatment train assessment tool

This paper outlines a rationale and scoring system for the stormwater treatment train assessment tool (STTAT) which is a proposed regulatory tool for Sustainable Urban Drainage Systems (SUDS). STTAT provides guidance and regulatory consistency for developers about the requirements of planners and the Scottish Environment Protection Agency (SEPA). The tool balances the risks of pollution to the receiving water-body with the treatment provided in a treatment train. It encourages developers to take SUDS into account early, avoiding any misunderstanding of SUDS requirements at the planning stage of a development. A pessimistic view on pollution risks has been adopted since there may be a change of land use on the development in the future. A realistic view has also been taken of maintenance issues and the ‘survivability’ of a SUDS component. The rationale for STTAT as a response to the requirements of the Water Framework Directive is explored and the individual scores are given in tabular format for receiving water and catchment risks. Treatment scores are proposed for single SUDS components as well as multiple components within treatment trains. STTAT has been tested on a range of sites, predominantly in Scotland where both development and receiving water information was known. The operational tool in use by SEPA is presented

Sustainable Urban Drainage Systems (SUDS) treatment train assessment tool

This paper outlines a rationale and scoring system for the stormwater treatment train assessment tool (STTAT) which is a proposed regulatory tool for Sustainable Urban Drainage Systems (SUDS). STTAT provides guidance and regulatory consistency for developers about the requirements of planners and the Scottish Environment Protection Agency (SEPA). The tool balances the risks of pollution to the receiving water body with the treatment provided in a treatment train. It encourages developers to take SUDS into account early, avoiding any misunderstanding of SUDS requirements at the planning stage of a development. A pessimistic view on pollution risks has been adopted since there may be a change of land use on the development in the future. A realistic view has also been taken of maintenance issues and the ‘survivability’ of a SUDS component. The development of STTAT as a response to the requirements of the Water Framework Directive is explored, the individual scores being given in tabular format for receiving water and catchment risks. Treatment scores are proposed for single SUDS components as well as multiple components within treatment trains. STTAT has been tested on a range of sites, predominantly in Scotland where both development and receiving water information was known. The operational tool in use by SEPA is presented