Feasibility study into accurately modelling sulphur dioxide flux in the lower atmosphere

Atmospheric pollutants are of concern for both their effects on human health and on plants and crops. Since the 1960s monitoring networks have been created, linked to international protocols regulating emissions of pollutants such as sulphur and nitrogen and also to validation studies of large-scale atmospheric transport models. One such monitoring site in the UK is at Auchencorth Moss, close to Edinburgh, where routine half-hourly measurements of sulphur dioxide are made. The time series shows a large amount of variation, and it is of interest to explore any trend in the pollutant level along with any presence of seasonal and diurnal cycles and to draw comparisons with pollutant transport model predictions. However, before carrying out such analysis, it is necessary to investigate the sources of variation. This thesis will consider the nature of the calculation of the sulphur dioxide flux, based on three simultaneous concentration measurements corrected for stability height. The need to calculate a slope estimate based on three points led to some difficulties and these were looked at to see whether these were creating difficulty when it came to modelling the fluxes. It was concluded that there were a high proportion of fluxes calculated using slope estimates with high R2 values and so any difficulty might lie in the actual data themselves rather than any technicalities in the calculations used to define the flux. From there, each variable involved in the calculation of the flux was studied, using approaches such as signal-to-noise ratios and sensitivity analysis. From these it was seen where most variation was occurring. Signal-to-noise ratio techniques did not work very well with the very low data measurements collected, which was disappointing but the values collected were generally very low suggesting a large level of noise in the data. Sensitivity analysis helped to show where most of the variation lay. Using a sampling based method it was shown that most of the variation lay in the gas concentrations themselves rather than any of the other variables involved in the calculation of the flux. This led to the conclusion that the gas concentrations rather than anything else were contributing to the difficulty of modelling sulphur dioxide fluxes. This suggested that there might be a possibility that there was no problem in the data collection approach or calculations of a flux, but perhaps the data itself was too variable to be modelled. Chaos theory offers a different approach to the analysis of time-series and this thesis explores the use of the Lyapunov exponent to investigate chaotic behaviour over different aggregated timescales. The chaos definition used was the popular “Sensitivity based on initial conditions” approach favoured by most people in this field. Looking at how quickly two data points placed very closely together could diverge after a certain time period would show whether any predictions made would be highly susceptible to any variation would be a very useful finding. Using three different techniques gave disappointing results however. The techniques all produced results which were sometimes conflicting with each other and none of which gave any convincing argument for, or against, the existence of chaos. This led to two potential conclusions. One being that the data were very noisy, but predictable underneath this, or methods of estimating chaotic behaviour can be flawed. This thesis also looks at how Extreme Value Analysis can be used on very noisy environmental time series and how useful it can be in explaining the behaviour of the larger values measured. In this study there were some large peaks in each of the years when looking at a time series analysis. These values were studied separately from the data using Generalised Extreme Value theory and the General Pareto Distribution. The Pareto distribution approach was concluded to give the better insight into the data. This was shown to model the extreme values reasonably well though both options could be taken as valid from these approaches. Finally the measured and modelled data (collected from a Europe-wide model) were compared and analysed to see how well they compare and what techniques from each of the previous analyses can be used to bring them closer together. These tended to show that the two data sets (modelled and measured) did not match up particularly well. Techniques such as a Bland-Altman analysis and many comparison diagnostic tests were analysed to see whether there were differences between the two. Even when some findings from earlier chapters were applied to the data such as applying a minimum R2 to any slope estimates did not help

First experimental observation of the aquatic propulsion caused by localised flexural waves in immersed structures

The present paper reports the results of the first experimental observation of the wave-like aquatic propulsion suitable for man-inhabited marine vessels. The idea of this propulsion, first published by one of the present authors (V.V.K.) more than 10 years ago, is based on employing localised flexural elastic waves propagating along edges of wedge-like elastic structures. Such wave-supporting structures can be attached to a body of a small ship or a submarine as keels or wings and used for the propulsion. To verify the idea experimentally, the first working prototype of a small catamaran using the above-mentioned wave-like propulsion via the attached rubber keel has been build and tested. The test results have shown that the catamaran was propelled quite efficiently and could achieve the speed of about 36 cm/s, i.e. approximately one length of the vessel per second. The reported proof of the viability of the idea of wave-like propulsion as alternative to a propeller may open new opportunities for marine propulsion which can have far reaching implications

Experimental confirmation of the propulsion of marine vessels employing guided flexural waves in attached elastic fins

This paper describes the results of the first experimental verification of the idea of wave-like aquatic propulsion of manned marine vessels first published by one of the present authors (V.V.K.) in 1994. The idea is based on employing the unique type of guided flexural elastic waves propagating along edges of immersed wedge-like structures attached to a body of a small ship or a submarine as keels or wings and used for the propulsion. The principle of employing such guided flexural waves as a source of aquatic propulsion is similar to that used in nature by stingrays. It is vitally important for the application of this idea to manned vessels that, in spite of vibration of the fins, the main body of the craft remains undisturbed as the energy of guided elastic waves is concentrated away from it. The main expected advantages of this new propulsion method over the existing ones, e.g. jets and propellers, are the following: it is quiet, and it is environmentally friendly and safe for people and wildlife. T

Experimental investigation of the aquatic propulsion caused by localised flexural wave propagation in immersed wedges and plates

Experimental investigation of the aquatic propulsion caused by localised flexural wave propagation in immersed wedges and plate

A comparison of the benzylic and the allylic group as a donor in the formal [4+2] cycloaddition to tetrahydropyrans using donor-acceptor cyclobutanes

The allyl group was shown to be preferred over the benzyl group as a donor in the formal [4+2]-cycloaddition reaction between a donor-acceptor cyclobutane and various aldehydes to give tetrahydropyrans

A biosynthetically inspired route to substituted furans using the Appel reaction: total synthesis of the furan fatty acid F₅

Appel reaction conditions have been harnessed to affect a mild biosynthetically inspired dehydration of endoperoxides to deliver multi-substituted electron rich furans. Unlike traditional dehydrative procedures, this method is metal and acid free, and can be achieved under redox neutral conditions. It is general for a range of aryl and alkyl substituted endoperoxides, and is functional group tolerant. Furthermore, this procedure has been used to deliver an effective total synthesis of the furan fatty acid (FFA) F5

A mild Lewis acid mediated epoxy-ester to bicyclic ortho ester rearrangement

A mild Lewis acid mediated epoxy-ester to bicyclic ortho ester rearrangemen

Indium-mediated 2-oxonia cope rearrangement of 1,4-dienols to 1,3-dienols

An indium-mediated isomerization of 1,4-dienols to 1,3-dienols is described. This procedure consists of the addition of pentadienylindium, in a protic solvent, to aldehydes giving the kinetic γ-allylation product in high yields. The subsequent conversion of this γ-allylation product to its thermodynamic 1,3-dienol α-isomer can be achieved by its exposure to indium triflate in the presence of a substoichiometric amount of aldehyde at room temperature. This transformation exhibited moderate to good substrate scope and has been shown to proceed by a 2-oxonia Cope rearrangement

Preparation of highly substituted tetrahydropyrans via a metal assisted dipolar cycloaddition reaction

A range of highly substituted tetrahydropyrans have been prepared by reaction of a donor-acceptor cyclobutane, where the donor is a metal-alkyne complex, with an aldehyde under Lewis 10 acid conditions