An accurate calculation of the exciton ground and excited states in AlGaAs and InGaAs coupled quantum wells (CQWs) in an external electric field is presented. An efficient and straightforward algorithm of solving the Schrödinger equation in real space has been developed and exciton binding energies, oscillator strengths, lifetimes, and absorption spectra are calculated for applied electric fields up to 100 kV/cm. It is found that in symmetric 8-4-8 nm GaAs/Al0.33Ga0.67As CQW structure, the ground state of the system switches from direct to indirect exciton at approximately 5 kV/cm with dramatic changes of its binding energy and oscillator strength while the bright excited direct-exciton state remains almost unaffected. It is shown that the excitonic lifetime is dominated either by the radiative recombination or by tunneling processes at small/large values of the electric field, respectively. The calculated lifetime of the exciton ground state as a function of the bias voltage is in a quantitative agreement with low-temperature photoluminescence measurements. We have also made freely available a numerical code for calculation of the optical properties of direct and indirect excitons in CQWs in an electric field.

An approach for the simulation of three-dimensional field-scale coupled thermo-hydro-mechanical problems is presented, including the implementation of parallel computation algorithms. The approach is designed to allow three-dimensional large-scale coupled simulations to be undertaken in reduced time. Owing to progress in computer technology, existing parallel implementations have been found to be ineffective, with the time taken for communication dominating any reduction in time gained by splitting computation across processors. After analysis of the behavior of the solver and the architecture of multicore, nodal, parallel computers, modification of the parallel algorithm using a novel hybrid message passing interface/open multiprocessing (MPI/OpenMP) method was implemented and found to yield significant improvements by reducing the amount of communication required. This finding reflects recent enhancements of current highperformance computing architectures. An increase in performance of 500% over existing parallel implementations on current processors was achieved for the solver. An example problem involving the Prototype Repository experiment undertaken by the Swedish Nuclear Fuel and Waste Management Co. [Svensk Kärnbränslehantering AB (SKB)] in Äspö, Sweden, has been presented to demonstrate situations in which parallel computation is invaluable because of the complex, highly coupled nature of the problem.

|Abstract|A new data analysis toolkit is presented, suitable for the analysis of large-scale, long-term datasets and the phenomenon/anomalies they possess. The toolkit aims to expose and quantify scientific information in a number of forms contained within a time-series based dataset in a quantitative and rigorous manner, reducing the subjectivity of observations made, thereby supporting the scientific observer. The features contained within the toolkit include the ability to handle non-uniform datasets, time-series component determination, frequency component determination, feature/event detection and characterisation/parameterisation of local behaviours. An application is presented of a case study dataset arising from the 'Lasgit' experiment.

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A hybrid MPI/OpenMP method of parallelising a bi-conjugate gradient iterative solver for coupled thermo-hydro-mechanical finite-element simulations in unsaturated soil is implemented and found to be efficient on modern parallel computers. In particular, a new method of parallelisation using a hybrid multi-threaded and message-passing approach depending on calculation size was implemented yielding better performance over more processing units. This was tested on both an Opteron 2218 2.6GHz Dual-Core processor based system with a Gigabit Ethernet interconnect and an Intel Xeon (Harpertown / Seaburg) 3.0GHz Quad-Core processor based system with an InfiniBand Connect-X interconnect. The impact of the experimental results reflect on the scalability of field-scale simulations with a higher resolution both spatially and temporally.