No description available.

In this thesis we provide a better understanding of the role of the inter-cluster filamentary environment in the evolution of galaxy properties, relating that to the physical mechanisms involved. We examine a poorer supercluster structure and describe how it compares with the richer regime, deciding whether the same processes are responsible for driving galaxy evolution in both cases. We develop a new approach to automated galaxy morphology classification, undertake an extensive observational survey of a nearby supercluster and investigate the evolution of galaxy properties within this structure, considering the filamentary environments that we confirm exist. Firstly, we present an application of Mathematical Morphology (MM) for the classification of astronomical objects, both for star/galaxy differentiation and galaxy morphology classification. We demonstrate that, for CCD images, 99.3 ± 3.8% of galaxies can be separated from stars using MM, with 19.4±7.9% of the stars being misclassified. We demonstrate that, for photographic plate images, the number of galaxies correctly separated from the stars can be increased using our MM diffraction spike tool, which allows 51.0±6.0% of the high-brightness galaxies that are inseparable in current techniques to be correctly classified, with only 1.4 ± 0.5% of the high-brightness stars contaminating the population. We demonstrate that elliptical (E) and late-type spiral (Sc-Sd) galaxies can be classified using MM at an accuracy of 91.4 ± 7.8%. It is a method involving less ‘free parameters’ than current techniques, especially automated machine learning algorithms. The limitations of MM due to seeing and distance are also discussed. We examine various star/galaxy differentiation and galaxy morhpology classification techniques commonly used today, and show that the above MM techniques compare very favourably. Secondly, we present a wide-field photometric and spectroscopic study of the supercluster SCL266 (z = 0.068). We have obtained CCD imaging in B-, R- and I-bands covering 5 clusters within the structure, and spectroscopy within the region of 3 of the clusters and the filamentary environment between them. We have over 950 redshifts obtained and 161 galaxies confirmed as members of the supercluster structure. The galaxy morphologies are derived using the MM techniques we have developed. We show that the population of passive, early-type galaxies extends into the dense regions of the filaments and is not just confined to the higher-density clusters, indicating that the denser filamentary environment hastens the galaxy evolution within it. The star-forming, late-type galaxies are distributed throughout the entirety of the supercluster structure. We show that both the mean star formation rate and the fraction of star-forming galaxies decrease strongly as a function of distance along the filaments towards the cluster centres. Given these observations we conclude that the evolution occurring within this poor supercluster begins within the filaments up to 4 Mpc away from the cluster centres, and is driven by long time-scale mechanisms involving encounters between neighbouring galaxies.

No description available.

In this thesis, we look at how the Cross-Entropy (CE) method can be used to solve various optimisation and estimation problems in telecommunication systems and network planning, especially in the presence of noise. In Chapter 2, we mention what comprises optimisation problems. Various optimisation problems, such as constrained optimization and convex optimisation, are discussed. We also address noisy optimisation and how dealing effectively with noise plays a crucial role in locating a global optimal solution. A brief overview of three algorithms that have successfully been applied to noisy optimisation problems is also given. Chapter 3 explores a short overview of the methodology behind the CE method. We discuss how the CE method requires two simple iterative stages to locate an optimal "degenerate" sampling distribution, and hence an optimal solution to the optimisation problem. We also show how a simple modification of the algorithm can tackle noisy optimisation problems. Numerical experiments for solving both non-noisy and noisy multi-extremal continuous optimisation problems are conducted. Three test functions are used to investigate the performance of the CE algorithm on both non-noisy and noisy cases. The results suggest that the proposed algorithm can locate a global optimal solution accurately. Also, we show that the performance of the CE algorithm can be improved using the injection method. Chapter 4 and Chapter 5 discuss two types of the Network Planning Problem (NPP): single-type NPP and multi-type NPP. The aim is to determine which links in the system should be purchased in order to provide the highest possible service to the consumers, subject to a constraint on the total budget. We introduce various CE-based algorithms to tackle such non-linear combinatorial optimisation problem. Numerical experiments suggest that the proposed algorithms perform effectively and reliably in all test cases. Chapter 6 is concerned with estimating the blocking probabilities in circuit switched networks. We look at how Importance Sampling and Sequential Importance Sampling can be used to estimate the blocking probabilities. Here, the CE method is used to find optimal sampling parameters to be used in Importance Sampling and Sequential Importance Sampling. Numerical experiments suggest that Sequential Importance Sampling achieves a variance reduction over Importance Sampling in almost all cases at a cost of increased simulation time. Using CE further increases the efficiency of both.

In this thesis we provide a better understanding of the role of the inter-cluster filamentary environment in the evolution of galaxy properties, relating that to the physical mechanisms involved. We examine a poorer supercluster structure and describe how it compares with the richer regime, deciding whether the same processes are responsible for driving galaxy evolution in both cases. We develop a new approach to automated galaxy morphology classification, undertake an extensive observational survey of a nearby supercluster and investigate the evolution of galaxy properties within this structure, considering the filamentary environments that we confirm exist. Firstly, we present an application of Mathematical Morphology (MM) for the classification of astronomical objects, both for star/galaxy differentiation and galaxy morphology classification. We demonstrate that, for CCD images, 99.3 ± 3.8% of galaxies can be separated from stars using MM, with 19.4±7.9% of the stars being misclassified. We demonstrate that, for photographic plate images, the number of galaxies correctly separated from the stars can be increased using our MM diffraction spike tool, which allows 51.0±6.0% of the high-brightness galaxies that are inseparable in current techniques to be correctly classified, with only 1.4 ± 0.5% of the high-brightness stars contaminating the population. We demonstrate that elliptical (E) and late-type spiral (Sc-Sd) galaxies can be classified using MM at an accuracy of 91.4 ± 7.8%. It is a method involving less ‘free parameters’ than current techniques, especially automated machine learning algorithms. The limitations of MM due to seeing and distance are also discussed. We examine various star/galaxy differentiation and galaxy morhpology classification techniques commonly used today, and show that the above MM techniques compare very favourably. Secondly, we present a wide-field photometric and spectroscopic study of the supercluster SCL266 (z = 0.068). We have obtained CCD imaging in B-, R- and I-bands covering 5 clusters within the structure, and spectroscopy within the region of 3 of the clusters and the filamentary environment between them. We have over 950 redshifts obtained and 161 galaxies confirmed as members of the supercluster structure. The galaxy morphologies are derived using the MM techniques we have developed. We show that the population of passive, early-type galaxies extends into the dense regions of the filaments and is not just confined to the higher-density clusters, indicating that the denser filamentary environment hastens the galaxy evolution within it. The star-forming, late-type galaxies are distributed throughout the entirety of the supercluster structure. We show that both the mean star formation rate and the fraction of star-forming galaxies decrease strongly as a function of distance along the filaments towards the cluster centres. Given these observations we conclude that the evolution occurring within this poor supercluster begins within the filaments up to 4 Mpc away from the cluster centres, and is driven by long time-scale mechanisms involving encounters between neighbouring galaxies.

No description available.

No description available.

No description available.

Quantum information processing opens up completely new possibilities in communication and computation, that would be impossible in the realms of classical physics. While the benefits of quantum information processing are well understood in theory, it remains a formidable challenge to experimentally implement even simple quantum information processing tasks. Numerous physical architectures have been proposed for preparing and coherently manipulating quantum information. Amongst these, quantum optics has been identified as a particularly promising candidate. In particular this arises from the long decoherence times of single photon states, which can be used to encode logical qubits in a variety of ways. Nonetheless, there remain formidable challenges to implementing large scale quantum information processing using optical qubits. Most notably these include: the preparation of pure indistinguishable photons; efficient number-resolving photo-detection; mode-matching; photon loss; and the non-determinism of entangling gates. Any future large scale implementation of optical quantum information processing protocols will require significant advances on most, if not all these fronts. In this thesis we aim to present a comprehensive overview of the major requirements for optical quantum information processing, understand the effects they have, and how they can be modeled. From this we aim to understand what the realistic technological requirements are to achieve scalable optical quantum information processing, and, where possible, suggest means by which to help achieve these goals.

No description available.