Fine Scale Simulation of Fractured Reservoirs: Applications and Comparison

Imperial Users onl

J-Block Triassic Well Performance & Reservoir Heterogeneity

Imperial Users onl

From Quantified CTL to QBF

QCTL extends the temporal logic CTL with quantifications over atomic propositions. This extension is known to be very expressive: QCTL allows us to express complex properties over Kripke structures (it is as expressive as MSO). Several semantics exist for the quantifications: here, we work with the structure semantics, where the extra propositions label the Kripke structure (and not its execution tree), and the model-checking problem is known to be PSPACE-complete in this framework. We propose a model-checking algorithm for QCTL based on a reduction to QBF. We consider several reduction strategies, and we compare them with a prototype (based on the SMT-solver Z3) on several examples

Photoluminescence Characterization of Patterned Quantum dots and Inverse Quantum dots

The ever increasing demand for oil and its limited supply have forced us to look for alternate sources of energy. Solar energy offers a cheap, alternate form of energy. The efficiency of a solar cell is set by the Shockley-Queisser limit and is currently very low. New techniques to increase the efficiency of solar cells are being explored. Quantum dots and inverse quantum dots are promising future ways to increase the efficiency of solar cells through multiple exciton generation. In this thesis, the fabrication and characterization of defect-free quantum dots and anti-dots are discussed

A framework for analyzing hyper-viscoelastic polymers

Hyper-viscoelastic polymers have multiple areas of application including aerospace, biomedicine, and automotive. Their mechanical responses are therefore extremely important to understand, particularly because they exhibit strong rate and temperature dependence, including a low temperature brittle transition. Relationships between the response at various strain rates and temperatures are investigated and a framework developed to predict large strain response at rates of c. 1000 s$^{-1}$ and above where experiments are unfeasible. A master curve of the storage modulus's rate dependence at a reference temperature is constructed using a DMA test of the polymer. A frequency sweep spanning two decades and a temperature range from pre-glass transition to pre-melt is used. A fractional derivative model is fitted to the experimental data, and this model's parameters are used to derive stress-strain relationships at a desired strain rate.Comment: 6 pages, 11 figures, conference paper from ECCMR X, 2017, p529-53

Reconsidering the possibility of room temperature ferromagnetism in Mn doped Zirconium oxide

The possibility to induce long range ferromagnetic order by doping oxides with transition metal ions has become a very exciting challenge in the last decade. Theoretically, it has been claimed that Mn doped ZrO$_2$ could be a very promising spintronic candidate and that high critical temperatures could be already achieved even for a low Mn concentration. Some experiments have reported room temperature ferromagnetism (RT-FM) whilst some others only paramagnetism. When observed, the nature of RT-FM appears to be controversial and not clearly understood. In this study, we propose to clarify and shed light on some of theses existing issues. A detailed study of the critical temperatures and low energy magnetic excitations in Mn doped ZrO$_2$ is performed. We show that the Curie temperatures were largely overestimated previously, due to the inadequate treatment of both thermal and transverse fluctuations, and disorder. It appears that the Mn-Mn couplings can not explain the observed RT-FM. We argue, that this can be attributed to the interaction between large moments induced in the vicinity of the manganese. This is similar to the non-magnetic defect induced ferromagnetism reported in oxides, semiconductors and graphene/graphite.Comment: 13 pages, 7 figures, to appear in EP