DSpace Community:http://dspace1.isd.glam.ac.uk:80/dspace/handle/10265/1182016-02-06T07:10:30Z2016-02-06T07:10:30ZHeat of hydration of Portland Cement-Metakaolin-Fly ash (PC-MK-PFA) blendsSnelson, David. Ghttp://dspace1.isd.glam.ac.uk:80/dspace/handle/10265/7512015-03-27T10:01:28Z2015-03-27T00:00:00ZTitle: Heat of hydration of Portland Cement-Metakaolin-Fly ash (PC-MK-PFA) blends
Authors: Snelson, David. G
Abstract: In the present study two pozzolanic materials are used, Metakaolin (MK) and Fly Ash (PFA), as binary and ternary partial replacement binders with Portland cement (PC) to investigate their effect on the rate of heat evolution (dQ/dt in J/gh) during hydration, and the heat of hydration, (Q(t) in J/g). For binary PC–PFA blends PC hydration is enhanced in the very early stages of hydration, but at extended periods (up to 120 h) an increase in PFA replacement level causes a systematic reduction in heat output. For binary PC–MK blends the results suggest that the MK initially diminishes PC hydration but the subsequent pozzolanic reaction of MK increasingly contributes to the heat output causing some blends to exceed the heat output of the PC control. For both systems a principal controlling factor in the PC hydration rate (and the heat evolution rate) is the water requirement of the pozzolan, but for PC–MK blends the pozzolanic reaction of the MK makes a significant contribution to the heat output. However this reaction is controlled both by the availability of water and the supply of Ca2+ ions from the hydrating PC which introduces an increasing level of complexity to the heat output versus time profiles. When combining MK and PFA in ternary PC–MK–PFA blends the MK has a dominant influence on the heat output versus time profiles.2015-03-27T00:00:00ZUrban Population Distribution Models and Service Accessibility EstimationLangford, MitchelHiggs, Garyhttp://dspace1.isd.glam.ac.uk:80/dspace/handle/10265/7352013-12-17T01:00:25Z2013-12-16T00:00:00ZTitle: Urban Population Distribution Models and Service Accessibility Estimation
Authors: Langford, Mitchel; Higgs, Gary
Abstract: This paper examines the influence of alternative population distribution models on GIS-based spatial accessibility analyses using the two-step Floating Catchment Analysis technique. Two population models were tested: the de facto standard of even-distribution within census tracts and a dasymetric-based approach. The latter builds on previous research through the use of a novel methodology that integrates raster map data with a recently built mailing information database in order to enhance the precision with which residential areas are identified. Analysis was conducted for a case study area (Cardiff, South Wales) in order to examine variations in accessibility to a number of public services in the city. The dasymetric model showed a general tendency to report lower accessibility scores, but detailed patterns depended on local factors and, to some extent, on modelling assumptions and methodological issues. A paired T-Test analysis demonstrated that significant differences in outcomes were dependant on the population model adopted. Accessibility-based measures are increasingly being incorporated into deprivation indicators and the paper concludes by suggesting that, if such analysis is to inform urban planning, local service provision and the spatial allocation of financial resources, greater attention needs to be given to the method of population representation utilised in such models.2013-12-16T00:00:00ZPoiseuille flow of a smectic a liquid crystalWalker, Alanhttp://dspace1.isd.glam.ac.uk:80/dspace/handle/10265/7302013-12-17T01:00:23Z2013-12-16T00:00:00ZTitle: Poiseuille flow of a smectic a liquid crystal
Authors: Walker, Alan
Abstract: This article considers the dynamics of smectic A liquid crystals subjected to Poiseuille flow. Linearised governing equations are constructed using a recent dynamic theory for Smectic A [1]. These equations are solved analytically and the consequent solutions are then calculated for some typical experimental data in order to determine the explicit flow behaviour. Stability of flow and layer structure solutions are proved. Results show how the response time for small perturbations to the smectic layers depends upon the permeation constant and the layer compression modulus. [1] I.W. Stewart, Dynamic theory for smectic A liquid crystals, Continuum Mech. Thermodyn. 18 (2007) 343–360.2013-12-16T00:00:00ZAcoustic waves in compressible planar layered smectic liquid crystalsWalker, Alanhttp://dspace1.isd.glam.ac.uk:80/dspace/handle/10265/7292013-12-17T01:00:23Z2013-12-16T00:00:00ZTitle: Acoustic waves in compressible planar layered smectic liquid crystals
Authors: Walker, Alan
Abstract: A dynamic theory for compressible smectic C (SmC) liquid crystals is postulated following previous work by Leslie, Stewart and Nakagawa [1], Nakagawa [2,3] and de Gennes [4]. This theory is then implemented with a constructed bulk elastic energy and asymmetric stress tensor to describe a system of planar layered SmC liquid crystals undergoing various undulation modes. We show that previous work on smectic~A (SmA) liquid crystals [4] can be expanded for SmC and consolidated. Novel and confirming estimates for SmC material parameter values are produced by considering the dependence of the system on these parameters. [1] F. M. Leslie, I. W. Stewart, and M. Nakagawa, A continuum theory for smectic C liquid crystals, Mol. Cryst. Liq. Cryst., 198 (1991), pp. 443-454. [2] M. Nakagawa, A hydrodynamic theory of compressible SmC* liquid crystals, J. Phys. Soc. Japan, 65 (1996), pp. 100-106. [3] M. Nakagawa, A hydrodynamic theory of compressible SmC* liquid crystals, J. Non-Newtonian Fluid Mech., 119 (2004), pp. 123-129. [4] P. G. de Gennes and J. Prost, The Physics of Liquid Crystals, Oxford University Press, Oxford, second ed., 1993.2013-12-16T00:00:00Z