Structure and energy relationships in ice and crystalline hydrates.

Computer simulations of the various phases of ice have been carried out using potential methods and density functional theory. Plane wave DFT and subsequent Wannier transformations of the Kohn-Sham orbitals were used to obtain highly localised orbitals, which were treated as molecular orbitals in the calculation of molecular multipoles. Using these multipoles it has been shown that the energy differences, calculated using DFT, between different proton topologies of ice VII and Ih are reproduced when the interaction electrostatic potential energy is calculated up to terms in (1/r6) and thus that the driving force for proton ordering is electro static. Armed with this knowledge, successful blind predictions, which have been experimentally verified, of the proton ordered forms of ice V and XII (ices XIII and XIV respectively) have been made using plane wave DFT. The recently developed TIP6P potential has been modified so as to reproduce the correct structure for ice XI, the proton ordered form of ice Ih, and to reproduce the DFT energy differences between different hydrogen bonding topologies. Total energy calculations, using this potential, show that the surface energy depends strongly on the hydrogen bond topology exposed at the surface. In particular surfaces on which under-coordinated protons are clustered have high energies. Monte Carlo calculations have shown that the hydrogen bond topology adopted by ice, both at the surface and in the bulk, depends on the temperature. A comparison of the structures that are possible to make out of silica and ice has been undertaken in the hope that new ice and silica phases can be identified. This comparison is possible because both silica and water form the backbones of 4-connected nets. DFT calculations have shown that the energy maps of the various four connected nets are very similar for both structures, with any differences arising because of the greater flexibility of the O-Si-O angle in silica. Furthermore, this analysis has highlighted a number of potential new ice phases and led to the proposal of a synthetic route to a new clathrate based on the zeolite framework SGT

Theory of measurement-based quantum computing

In the study of quantum computation, data is represented in terms of linear operators which form a generalized model of probability, and computations are most commonly described as products of unitary transformations, which are the transformations which preserve the quality of the data in a precise sense. This naturally leads to "unitary circuit models", which are models of computation in which unitary operators are expressed as a product of "elementary" unitary transformations. However, unitary transformations can also be effected as a composition of operations which are not all unitary themselves: the "one-way measurement model" is one such model of quantum computation. In this thesis, we examine the relationship between representations of unitary operators and decompositions of those operators in the one-way measurement model. In particular, we consider different circumstances under which a procedure in the one-way measurement model can be described as simulating a unitary circuit, by considering the combinatorial structures which are common to unitary circuits and two simple constructions of one-way based procedures. These structures lead to a characterization of the one-way measurement patterns which arise from these constructions, which can then be related to efficiently testable properties of graphs. We also consider how these characterizations provide automatic techniques for obtaining complete measurement-based decompositions, from unitary transformations which are specified by operator expressions bearing a formal resemblance to path integrals. These techniques are presented as a possible means to devise new algorithms in the one-way measurement model, independently of algorithms in the unitary circuit model.Comment: Ph.D. thesis in Combinatorics and Optimization. 199 pages main text, 26 PDF figures. Official electronic version available at http://hdl.handle.net/10012/413

On optimal and near-optimal algorithms for some computational graph problems

PhD ThesisSome computational graph problems are considered in this thesis and algorithms for solving these problems are described in detail. The problems can be divided into three main classes, namely, problems involving partially ordered sets, finding cycles in graphs, and shortest path problems. Most of the algorithms are based on recursive procedures using depth-first search. The efficiency of each algorithm is derived and it can be concluded that the majority of the proposed algorithms are either optimal and near-optimal within a constant factor. The efficiency of the algorithms is measured by the time and space requirements for their implementation.Conselho Nacional de Pesquisas,Brazil: Universidade Federal do Rio de Janeiro, Brazil

International Conference on Civil Infrastructure and Construction (CIC 2020)

This is the proceedings of the CIC 2020 Conference, which was held under the patronage of His Excellency Sheikh Khalid bin Khalifa bin Abdulaziz Al Thani in Doha, Qatar from 2 to 5 February 2020. The goal of the conference was to provide a platform to discuss next-generation infrastructure and its construction among key players such as researchers, industry professionals and leaders, local government agencies, clients, construction contractors and policymakers. The conference gathered industry and academia to disseminate their research and field experiences in multiple areas of civil engineering. It was also a unique opportunity for companies and organizations to show the most recent advances in the field of civil infrastructure and construction. The conference covered a wide range of timely topics that address the needs of the construction industry all over the world and particularly in Qatar. All papers were peer reviewed by experts in their field and edited for publication. The conference accepted a total number of 127 papers submitted by authors from five different continents under the following four themes: Theme 1: Construction Management and Process Theme 2: Materials and Transportation Engineering Theme 3: Geotechnical, Environmental, and Geo-environmental Engineering Theme 4: Sustainability, Renovation, and Monitoring of Civil InfrastructureThe list of the Sponsors are listed at page 1