Energy Efficency In Housing: An Evaluation Of The Importance Of Increased Wall Thickness

In April 2002 revisions to Part L of the Building Regulations were introduced, to improve the energy efficiency of UK buildings. For many housing schemes using traditional masonry cavity walls this may result in an increased cavity width and a consequent increase in the dwelling footprint. The potential impact that this may have on site utilisation, particularly in the light of planning guidance aimed at increasing site densities, has raised concern within the development community. Developers argue that even minor increases in wall thickness may reduce the number of dwellings on sites, thereby reducing overall profitability. This paper analyses these concerns by investigating the impact of increased wall thickness in the context of two developments constructed in the late 1990s. The existing site layouts were analysed under different footprint assumptions and an assessment made of the capacity of the layout to accommodate footprint increases. The theoretical analysis demonstrates that dwelling numbers are unlikely to be reduced as a result of the standards introduced in 2002. It is only when anticipated future improved standards are applied that dwelling numbers may be affected. However, the paper demonstrates also that dwelling loss is not inevitable and that it is perfectly possible to produce very low energy housing, while still achieving densities in line with planning requirements and with no reduction in the overall quality of a scheme. In the end it is not a matter of wall thickness but of good site layout and good house type design

Cosmic ray acceleration in young supernova remnants

We investigate the appearance of magnetic field amplification resulting from a cosmic ray escape current in the context of supernova remnant shock waves. The current is inversely proportional to the maximum energy of cosmic rays, and is a strong function of the shock velocity. Depending on the evolution of the shock wave, which is drastically different for different circumstellar environments, the maximum energy of cosmic rays as required to generate enough current to trigger the non-resonant hybrid instability that confines the cosmic rays follows a different evolution and reaches different values. We find that the best candidates to accelerate cosmic rays to ~few PeV energies are young remnants in a dense environment, such as a red supergiant wind, as may be applicable to Cassiopeia A. We also find that for a typical background magnetic field strength of 5 microG the instability is quenched in about 1000 years, making SN1006 just at the border of candidates for cosmic ray acceleration to high energies.Comment: 14 pages, 8 figures. Accepted for publication in MNRA

Magnetic field amplification by cosmic rays in supernova remnants

Magnetic field amplification is needed to accelerate cosmic cays to PeV energies in supernova remants. Escaping cosmic rays trigger a return current in the plasma that drives a non-resonant hybrid instability. We run simulations in which we represent the escaping cosmic rays with the plasma return current, keeping the maximum cosmic ray energy fixed, and evaluate its effects on the upstream medium. In addition to magnetic field amplification, density perturbations arise that, when passing through the shock, further increase amplification levels downstream. As the growth rate of the instability is most rapid for the smaller scales, the resolution is a limiting factor in the amplification that can be reached with these simulations.Comment: 4 pages, 2 figures, to appear in the proceedings of the conference "370 years of Astronomy in Utrecht", eds. G. Pugliese, A. de Koter and M. Wijbur

Confining the high-energy cosmic rays

Diffusive shock acceleration is the prime candidate for efficient acceleration of cosmic rays. Galactic cosmic rays are believed to originate predominantly from this process in supernova remnant shock waves. Confinement of the cosmic rays in the shock region is key in making the mechanism effective. It has been known that on small scales (smaller than the typical gyroradius) high-amplitude non-resonant instabilities arise due to cosmic ray streaming ahead of the shock. For the efficiency of scattering of the highest energy cosmic rays it is of interest to determine the type of instabilities that act on longer length scales, i.e. larger than the cosmic ray gyroradius. We will present the results of our analysis of an instability that acts in this regime and will discuss its driving mechanism and typical growth times.Comment: 4 pages, 1 figure. Proceedings for the conference on Cosmic Rays and the Interstellar Medium (CRISM) in June 2011, Montpellier, France. To appear in MSA

Ontology learning for semantic web services

Semantic Web Services promise automatic service discovery and composition, relying heavily on domain ontology as a core component. With large Web Service repository, manual ontology development is proving a bottleneck (with associated expense and likely errors) to the realisation of a semantic Web of services. Providing the appropriate tools that assist in and automate ontology development is essential for a dynamic service vision to be realised. As a statement of research-in-progress, this paper proposes combining different ontology learning paradigms in Web Services domain, highlighting the need for further research that accommodates the variation in Web Service descriptive and operational sources. A research agenda is proposed that recognises this variation in artefacts as they are selected, pre-processed and analyzed by ontology learning techniques

Maximal abelian and Curci-Ferrari gauges in momentum subtraction at three loops

The vertex structure of QCD fixed in the maximal abelian gauge (MAG) and Curci-Ferrari gauge is analysed at two loops at the fully symmetric point for the 3-point functions corresponding to the three momentum subtraction (MOM) renormalization schemes. Consequently the three loop renormalization group functions are determined for each of these three schemes in each gauge using properties of the renormalization group equation.Comment: 23 latex pages, 4 figures, anc directory contains txt files with electronic version of renormalization group functions, coupling constant mappings, conversion functions and amplitudes in analytic form for each gaug

Bilinear quark operator renormalization at generalized symmetric point

We compute Green's functions with a bilinear quark operator inserted at non-zero momentum for a generalized momentum configuration to two loops. These are required to assist lattice gauge theory measurements of the same quantity in matching to the high energy behaviour. The flavour non-singlet operators considered are the scalar, vector and tensor currents as well as the second moment of the twist-2 Wilson operator used in deep inelastic scattering for the measurement of nucleon structure functions.Comment: 19 latex pages, 4 figures, anc directory contains electronic version of amplitude