First, I would like to thank to Dimka Karastoyanova and Mariano Cilia for all the fruitful discussions, their guidance and support through the course of this project. Thanks also to Prof. Alejandro Buchmann who sponsored my stay at Technische Universität Darmstadt during the spring of 2004. The special thanks go to my advisor, Mariano Cilia, who has made all this possible. Finally, I’d like to thank to my family for all these years of support.

Abstract Supporting database schema evolution repre-sents a long-standing challenge of practical and theoretical importance for modern information systems. In this paper, we describe techniques and systems for automating the critical tasks of migrating the database and rewriting the legacy

As this master thesis marks the end of my studies at Delft University of Technology, I would like to use this opportunity and thank everyone who has influenced my two-year journey. Those last two years have not been easy. In fact, it has been the most challenging, stressful, and at the same time- the most inspiring, productive, and exciting journey. Journey, which has completely changed my life and has prepared me for new challenges and opportunities. I owe a very special debt to the ex president of Georgia – Mikheil Saakashvili, for initiating a scholarship program for Georgian students abroad, willing to pursue master’s degree. I would like to thank Mr. Saakashvili for giving me a chance to be one of those students, and for fully sponsoring my studies at TU Delft. I must express special gratitude to my graduation committee for being way more supportive then I could ever imagine. I would like to thank them for all their feedback, support, and encouragement, for being very understanding, and shortly, for making it possible for me to finalize my thesis and to graduate. I would like to acknowledge the selfless help and support of my supervisor – Dr. Huib Aldewereld. His guidance and support encouraged me to be motivated and to keep working on the thesis. I would like to thank him for all his time that he has spent on reading my thesis, on giving me direct comments, and further motivation. I had times when I felt lost in my own thesis, and I was ready to give up, but Dr. Aldewereld always managed to encourage and motivate me. I would like to thank him for arranging meetings (lots of meetings) with me to discuss my progress, whenever I asked for it, despite his very

Implementational aspects of code-based cryptography

I hereby declare that I have created this work completely on my own and used no other sources or tools than the ones listed, and that I have marked any citations accordingly. Hiermit versichere ich, dass ich die vorliegende Arbeit selbständig verfasst und keine anderen als die angegebenen Quellen und Hilfsmittel benutzt sowie Zitate kenntlich gemacht habe.

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Abstract not found

Fluorine gas is produced industrially by electrolysing hydrogen fluoride in a potassium acid fluoride electrolyte. Fluorine is produced at the carbon anode, while hydrogen is produced at the mild-steel cathode. The fluorine produced has a wide range of uses, most notably in the nuclear industry where it is used to separate 235U and 238U. The South African Nuclear Energy Corporation (Necsa) is a producer of fluorine and requested an investigation into the hydrodynamics of their electrolysis cells as part of a larger national initiative to beneficiate more of South Africa’s large fluorspar deposits. Due to the extremely corrosive and toxic environment inside a typical fluorine electrolysis reactor, the fluid dynamics in the reactor are not understood well enough. The harsh conditions make detailed experimental investigation of the reactors extremely dangerous. The objective of this project is to construct a model that can accurately predict the physical processes involved in the production of fluorine gas. The results of the simulation will be compared to experimental results from tests done on a lab-scale reactor. A good correlation

ACKNOWLEDGMENTS I would like to give many thanks to Dr. Shengli Fu and Dr. Yan Huang as my advi-

mcmxciv This thesis deals with combinatorics in connection with Coxeter groups, finitely generated but not necessarily finite. The representation theory of groups as nonsingular matrices over a field is of immense theoretical importance, but also basic for computational group theory, where the group elements are data structures in a computer. Matrices are unnecessarily large structures, and part of this thesis is concerned with small and efficient representations of a large class of Coxeter groups (including most Coxeter groups that anyone ever payed any attention to.) The main contents of the thesis can be summarized as follows. • We prove that for all Coxeter graphs constructed from an n-path of unlabelled edges by adding a new labelled edge and a new vertex (sometimes two new edges and vertices), there is a permutational representation of the corresponding group. Group elements correspond to integer n-sequences and the nodes in the path generate all n! permutations. The extra node has a more complicated action, adding a certain quantity to some of the numbers.