A capillary flow gas viscometer has been used to measure the shear viscosities of the hydrofluoroalkanes HFC 134a, HCFC 123, HCFC 124 and the ternary blend MP 39, at pressures up to 0.1 MPa relative to a nitrogen standard. Having applied small correction factors to the measured flow time data, the resultant viscosities are compared to those obtained by other workers (where possible) using alternative techniques. We calculate self diffusion coefficients and hard sphere collision diameters for the molecules within the rigorous Chapman-Enskog kinetic theory of gases, and calculate optimum well depths of the intermolecular interactions using the Extended Law of Corresponding States. The use of a Stockmayer potential energy function by other workers is discussed and within this, the Mason-Monchick approximation is applied to calculate the percentage effect of the dipole moment on the collision integral. In order to assess the affect to the atmospheric chlorine loading of the hydrochlorofluorocarbons measured above (HCFC 123. HCFC 124 and HCFC 22 in MP 39) as well as other halocarbons currentiy in use, two globally averaged mass balance models have been developed on a workstation spreadsheet to assess the future chlorine and bromine levels in the atmosphere and the sensitivity of those loadings to possible forcing factors. These models use production, growth, lifetime and concentration data for fourteen chlorocarbons and three bromocarbons and allow for characteristic emission profiles according to the use to which the halocarbon is applied. Current international agreement, ie. Montreal Protocol 3, is used as a reference level (in most cases), and the models have been used to assess tiiose scenarios which most influence the peak level of chlorine and bromine attained, when that peak occurs and the period of time before 'safe' levels are reached.

Diesel engines account for a large percentage of the particulates in urban city environments. Polycyclic aromatic compounds (PAC), some proven carcinogens, have been found on diesel particulates. The trace level nitro-PAC emissions, such as 1-nitropyrene and dinitropyrenes, contribute a large proportion of the mutagenicity in the particulates; in the case of 1-nitropyrene between 10 to 40% of the total mutagenicity of the particulate has been claimed. The potential health hazards of PAC require the levels and sources of such emissions to be evaluated over a range of speeds and loads. PAC emissions are dependant on the engine specification, such as normally aspirated compared with turbocharged, and the operating conditions (speed and load). The effect of such variables can be determined using emission profiling, in which profiles of the exhaust are compared at varying engine powers. In this way the effect of speed and load on the combustion efficiency can be established. Identification of PAC sources may be further complicated when engine sampling systems, such as the conventional dilution tunnel/filter system, are prone to artefact formation. This is especially relevant to secondary nitro-PAC emissions, which are prone to forming as artefacts of the filter installed in the dilution tunnel. In this study, organic emission maps were constructed using the unique total exhaust solvent-stripping apparatus (TESSA) developed at the University of Plymouth. TESSA allowed rapid sampling with a minimum potential for artefact formation. The close proximity of TESSA to the engine allowed the role of the combustion chamber in the formation of emissions to be evaluated. Primary organic emissions, such as pyrene, are derived from survival of compounds in the fuel/oil and by combustion generation. Establishment of emission maps for the primary emissions are vital to resolving the formation of secondary emissions, such as 1-nitropyrene. Profiling of primary emissions sampled 26 different speeds and loads using TESSA (sampling times as low as IS seconds). Following simple work-up, quantification of the o-alkanes was by gas chromatography with flame ionisation detection and PAH by gas chromatography/mass spectrometry operated in electron impact mode. Emissions were expressed as a recovery of the compound emitted as a percentage of the same compound entering the chamber in the fuel. The o-alkane and PAH emission maps correlated with the gaseous unburnt hydrocarbon emissions, indicating that fuel survival was an important source of emissions, whereas lubricating oil contributions were minimal. Fuel survival contributions decreased with load; at 1000 rpm the average PAH survival of 0.95% at idling decreased to 0.2% at full load. High survivals under idling was a consequence of the low chamber temperatures and air:fuel ratios mixed beyond the lean flammability limits, whereas at full load, the high temperatures resulted in the greatest combustion efficiency. The o-alkane emission trends replicated those of PAH; at 1000 rpm the average o-alkane survival was 0.48% at idle compared with 0.084% at full load. Correlations between the distribution of the emissions and fuel at high load, suggested fuel survival unchanged was responsible. At low loads the exhaust/fuel PAH ratios were more varied, with the range of percentage recoveries at low loads increasing with speed (difference between percentage recovery of fluorene and phenanthrene at idling for 1000 rpm and 3000 rpm was 0.05 and 0.18 respectively). At high load, the combustion environment can be envisaged as producing areas under which complete combustion and survival unchanged occur. In between the complete combustion and unburnt fuel zones, a narrow range of temperatures and time for combustion reduce the opportunity for combustion generation reactions and/or preferential survival. Low load at 3000 rpm may increase the intermediate zone, allowing preferential survival and/or combustion generation reactions to evolve. Possible pyrolytic cracking of o-alkanes and demethylation of PAH at low loads and 3000 rpm was evident. The optimum time, swirl, and temperature for efficient combustion at low loads was generated at 2000 rpm to 2500 rpm, whereas at the higher temperatures corresponding to high loads, the effect of speed was much smaller. The primary emissions map show engineering improvements, particularly at low loads, could be implemented to lower the PAH emissions. The correlation between the emissions and fuel input suggest modifications to the PAH content of fuels may lower emissions. The formation of secondary nitro- and oxy-PAC emissions is by transformation of primary emissions. In the case of nitro-PAC, nitration has been proposed to occur by free radical processes between PAH and oxides of nitrogen, NO,, within the chamber and by electrophilic substitution of PAH surviving combustion by nitrogen dioxide and nitric acid, via the nitronium ion. The combustion contribution to nitro-PAC emissions was investigated using an upgraded TESSA system, and 3 speeds at low, mid, and high NO, for each speed were sampled. Following initial extraction, concentration and clean-up of the samples, the nitro-PAC fractions of interest were isolated by normal phase high performance liquid chromatography. The nitro-PAC were identified and quantified by gas chromatography with electron capture detection, and gas chromatography/mass spectrometry operated in the negative ion chemical ionisation mode (the detection limits for both analytical systems was of the order of 40-50 pg of nitro-PAC standards injected). The profiling indicated that a proportion of the fuel underwent nitration within the combustion chamber across a range of speeds and loads. The extract concentrations (average of 5.3 ppm) found in this study were much lower than those previous found (ranging from 55 to 2280 ppm). The majority of the previous studies relied on sampling using dilution tunnel/filter systems, for which post combustion contributions are simulated; suggesting that a major source of nitro-PAC is derived from post-combustion nitration of PAH surviving combustion, some of which may be artefacts of the filter. Different speeds produced different trends for nitro-PAC emissions with respect to engine load. It was not until the high temperature speed of 3500 rpm was reached that both NO, and nitro-PAC increased with load (R-sq= 0.989 & p=0.067 for 1-nitronaphthalene & NO,). Nitro-PAC emissions at 3500 rpm were primarily the result of combustion chamber nitration of PAH at high NO. In the case of 1-nitropyrene, there was strong evidence to support pyrosynthetic contributions to the pyrene mass, which in turn became nitrated. The nitro-PAC emissions at low loads were the result of post-combustion nitration of PAH surviving combustion with the nitronium ion. The correlation of the PAH precursors to nitro-PAC in the fuel and nitro-PAC emissions suggest fuel modifications may to some extent lower the nitro-PAC emissions. The combustion generation of nitro-PAC at high engine powers may require post-combustion after treatment.

The ceramic glazing techniques of vapour glazing, reduction lustre, Raku and fuming all require specialised firing conditions with the use of potentially hazardous kiln atmospheres and specialist kiln designs for their successful execution. The technique of reduction lustre is an ancient, highly decorative technique in which pigments or glazes containing reducible metal oxides such as copper, silver and bismuth are subjected to a reducing atmosphere which results in the formation of stable iridescent lustrous colour effects. Conventionally hydrocarbons are used to produce a reducing atmosphere, the combustion of which can lead to potentially high levels of CO. This research has concentrated on the technique of reduction lustre with the aim of producing a safe, environmentally friendly firing system. Reduction lustre effects were reproduced using a 100 litre down draft gas kiln designed and constructed for the purpose. A 40 litre electric kiln was modified for use with reducing atmospheres and a laboratory muffle kiln was also adapted to provide closely controlled firing conditions. Alternative reducing atmospheres were assessed, consisting of either 5% H2 in N2 or hydrocarbon vapour in N2 The former is reliable, safe, environmentally friendly and is recommended for studio pottery use. A theoretical design for a reduction lustre kiln incorporating a gas control system based on the use of a 5% H2 in N2 gas mixture and a gas tight outer casing was developed. Thermoanalytical methods were used to investigate the reduction behaviour of raw materials, glazes and frits under different atmospheric conditions. Diffusional and topochemical models of reduction reactions occurring in a typical lustre glaze have been evaluated. In-glaze lustres reduce with thecharacteristics of diffusion processes. Water diffusion out of the glaze may be rate determining. Studies carried out using energy dispersive x-ray analysis andphoto electron spectroscopy show that lustres are associated with the presence of metallic copper, the actual colour being dependent on the surface concentration of the metal. The aesthetic results of the various firing methods developed were assessed using a perceptual study based on the use of a semantic differential test developed from a multiple sorting survey carried out using lustred tiles. The survey used both lustred tiles to represent a 2-dimensional surface and lustred vases which represented a 3-dimensional lustre glazed surface. The survey showed that statistically significant differences were observed between lustred ceramics fired in different systems, allowing comparisons to be made in an objective manner.

No description available.

No description available.

The presence of 'greenhouse gases' in the atmosphere has a warming effect on the biosphere, making the world habitable for life. Human activities, particularly energy use and deforestation, are increasing the concentration of these gases, and in particular carbon dioxide (CO₂). Many climatologists believe that the global temperature is beginning to rise as a result. The intergovernmental Panel on Climate Change (IPCC) has recommended that emissions of CO₂ be cut by 60 per cent in order to stabilise the atmospheric concenaation of this gas and to minimise the resulting disruption to the world's climate. Transport is currently Britain's fastest growing source of carbon dioxide, the principal anthropogenic greenhouse gas. An assessment is made of the relative contributions to CO2 emissions of different forms of travel, and trends in energy use are surveyed. Emissions of CO₂ from 'secondary' sources, such as vehicle production, are also examined. A computer model called SPACE is described, which was developed in order to assess CO₂ emissions under different policy scenarios up to the year 2025. A 'business as usual' scenario predicts that emissions will rise substantially, mainly as a result of an ongoing rise in road traffic. This contrasts with the Government's stated aim of stabilising emissions of CO₂ at the 1990 level by 2000. A modification of this scenario, in which technological improvements to vehicles are vigorously applied, shows a reduced growth in emissions. A third scenario then examines the effect of a combination of technological and demand management policies, and demonstrates a significant reduction in emissions. Scenario 3 adopts what are seen as fairly modest policy measures, making use of their synergistic effect. The main justification for this 'non-radical' approach is public and political acceptability. It is, however, recognised that most of the policy measures could be applied more vigorously if required If it is assumed that transport is allotted a less stringent target than other energy-consuming sectors, the reduction in emissions projected in Scenario 3 is consistent with the IPCC goal of atmospheric CO₂ stabilisation. Data sets compiled as part of the SPACE model can be made available on request.

No description available.

The hypothesis of this thesis is that the time-of-flight method of determining an estimate of the aerodynamic diameter of aerosol particles is fundamentally flawed when applied to non-spherical and/or non-unit density particles. Such a particle-sizing system, the TSI Aerodynamic Particle Sizer, is challenged with solid, non-spherical particles of known aerodynamic diameter to assess the influence of particle shape on instrument response. The aerodynamic diameter of the non-spherical particles is also determined under gravitational settling. Deposits that had been size-separated are resuspended for aerodynamic sizing by the APS. The experimental study is supplemented by a theoretical investigation of the relative effects of particle density and shape on APS-measured diameters. This is achieved through the development of a computational routine to calculate the trajectories of particles of various densities and shapes through the APS nozzle and sensing zone. The results of these calculations are compared with the experimentally-measured APS performance. The consequences for the traceability and accuracy of data measured using this technique are assessed in the light of the outcome of both aspects of the study.

No description available.

Thesis (Ph. D.)--University of Hawai'i, 1998. / Includes bibliographical references (p. 371-410).