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Abstract
The main theme of this thesis is about Graph Coloring Applications and Defining Sets in Graph Theory.
As in the case of block designs, finding defining sets seems to be difficult problem, and there is not a general conclusion. Hence we confine us here to some special types of graphs like bipartite graphs, complete graphs, etc.
In this work, four new concepts of defining sets are introduced:
• Defining sets for perfect (maximum) matchings
• Defining sets for independent sets
• Defining sets for edge colorings
• Defining set for maximal (maximum) clique
Furthermore, some algorithms to find and construct the defining sets are introduced. A review on some known kinds of defining sets in graph theory is also incorporated, in chapter 2 the basic definitions and some relevant notations used in this work are introduced.
chapter 3 discusses the maximum and perfect matchings and a new concept for a defining set for perfect matching.
Different kinds of graph colorings and their applications are the subject of chapter 4.
Chapter 5 deals with defining sets in graph coloring. New results are discussed along with already existing research results, an algorithm is introduced, which enables to determine a defining set of a graph coloring.
In chapter 6, cliques are discussed. An algorithm for the determination of cliques using their defining sets. Several examples are included.

The study of families of curves with prescribed singularities has a long tradition. Its foundations were laid by Plücker, Severi, Segre, and Zariski at the beginning of the 20th century. Leading to interesting results with applications in singularity theory and in the topology of complex algebraic curves and surfaces it has attained the continuous attraction of algebraic geometers since then. Throughout this thesis we examine the varieties V(D,S1,...,Sr) of irreducible reduced curves in a fixed linear system |D| on a smooth projective surface S over the complex numbers having precisely r singular points of types S1,...,Sr. We are mainly interested in the following three questions: 1) Is V(D,S1,...,Sr) non-empty? 2) Is V(D,S1,...,Sr) T-smooth, that is smooth of the expected dimension? 3) Is V(D,S1,...Sr) irreducible? We would like to answer the questions in such a way that we present numerical conditions depending on invariants of the divisor D and of the singularity types S1,...,Sr, which ensure a positive answer. The main conditions which we derive will be of the type inv(S1)+...+inv(Sr) < aD^2+bD.K+c, where inv is some invariant of singularity types, a, b and c are some constants, and K is some fixed divisor. The case that S is the projective plane has been very well studied by many authors, and on other surfaces some results for curves with nodes and cusps have been derived in the past. We, however, consider arbitrary singularity types, and the results which we derive apply to large classes of surfaces, including surfaces in projective three-space, K3-surfaces, products of curves and geometrically ruled surfaces.

In this thesis a new family of codes for the use in optical high bit rate transmission systems with a direct sequence code division multiple access scheme component was developed and its performance examined. These codes were then used as orthogonal sequences for the coding of the different wavelength channels in a hybrid OCDMA/WDMA system. The overall performance was finally compared to a pure WDMA system. The common codes known up to date have the problem of needing very long sequence lengths in order to accommodate an adequate number of users. Thus, code sequence lengths of 1000 or more were necessary to reach bit error ratios of with only about 10 simultaneous users. However, these sequence lengths are unacceptable if signals with data rates higher than 100 MBit/s are to be transmitted, not to speak about the number of simultaneous users. Starting from the well known optical orthogonal codes (OOC) and under the assumption of synchronization among the participating transmitters - justified for high bit rate WDM transmission systems -, a new code family called ?modified optical orthogonal codes? (MOOC) was developed by minimizing the crosscorrelation products of each two sequences. By this, the number of simultaneous users could be increased by several orders of magnitude compared to the known codes so far. The obtained code sequences were then introduced in numerical simulations of a 80 GBit/s DWDM transmission system with 8 channels, each carrying a 10 GBit/s payload. Usual DWDM systems are featured by enormous efforts to minimize the spectral spacing between the various wavelength channels. These small spacings in combination with the high bit rates lead to very strict demands on the system components like laser diode, filters, multiplexers etc. Continuous channel monitoring and temperature regulations of sensitive components are inevitable, but often cannot prevent drop downs of the bit error ratio due to aging effects or outer influences like mechanical stress. The obtained results show that - very different to the pure WDM system - by orthogonally coding adjacent wavelength channels with the proposed MOOC, the overall system performance gets widely independent from system parameters like input powers, channel spacings and link lengths. Nonlinear effects like XPM that insert interchannel crosstalk are effectively fought. Furthermore, one can entirely dispense with the bandpass filters, thus simplifying the receiver structure, which is especially interesting for broadcast networks. A DWDM system upgraded with the OCDMA subsystem shows a very robust behavior against a variety of influences.

Urban Design Guidelines have been used in Jakarta for controlling the form of the built environment. This planning instrument has been implemented in several central city redevelopment projects particularly in superblock areas. The instrument has gained popularity and implemented in new development and conservation areas as well. Despite its popularity, there is no formal literature on the Indonesian Urban Design Guideline that systematically explain its contents, structure and the formulation process. This dissertation attempts to explain the substantive of urban design guideline and the way to control its implementation. Various streams of urban design theories are presented and evaluated in term of their suitability for attaining a high urbanistic quality in major Indonesian cities. The explanation on the form and the practical application of this planning instrument is elaborated in a comparative investigation of similar instrument in other countries; namely the USA, Britain and Germany. A case study of a superblock development in Jakarta demonstrates the application of the urban design theories and guideline. Currently, the role of computer in the process of formulating the urban design guideline in Indonesia is merely as a replacement of the manual method, particularly in areas of worksheet calculation and design presentation. Further support of computer for urban planning and design tasks has been researched in developed countries, which shows its potential in supporting decision-making process, enabling public participation, team collaboration, documentation and publication of urban design decisions and so on. It is hoped that the computer usage in Indonesian urban design process can catch up with the global trend of multimedia, networking (Internet/Intranet) and interactive functions that is presented with examples from developed countries.