Master Degree / Yüksek Lisans Tezleri

Permanent URI for this collectionhttps://hdl.handle.net/11147/3008

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2003 - 200932010 - 20141

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Publisher: search.filters.publisher.Izmir Institute of TechnologySubject: search.filters.subject.Algorithms

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Now showing 1 - 4 of 4
  • Master Thesis
    Stacking Sequence Optimization of the Anti-Buckled Graphite/Epoxy Laminated Composites for Minimum Weight Using Generalized Pattern Search Algorithm
    (Izmir Institute of Technology, 2014) Boyacı, Hakan; Artem, Hatice Seçil; Artem, Hatice Seçil
    Composite materials have been increasingly used during the last decades due to their properties such as low weight, high stiffness, superior fatigue and corrosion resistance. They have been used in aerospace, automobile, marine applications and etc. Composite materials being an expensive but efficient technology to get minimum weight structures, it is logical to make an attempt to find out how to design properly optimum laminated composite plates with no reduction in their strength. The aim of the thesis is to find the optimum stacking sequence to obtain the minimum thickness (weight) of laminated composite plates in different loadings and plate dimensions under buckling constraint. Moreover, a comparison study of conventional and continuous designs are performed to determine the effect of stacking sequence on weight. The objective function is the critical buckling load factor. Fiber angles of the composite plates are taken as continuous design variables and the plate is assumed to be balance and symmetric. Composite plates made of graphite/epoxy have been considered in this thesis. A combination of Generalized Pattern Search Algorithm (GPSA) and Genetic Algorithm (GA) has been considered as an optimization method. All the results show that the loading conditions and dimensions of composite plates are significant in stacking sequences optimization of laminated composite materials in terms of maximum critical buckling load factor and minimum thickness.
  • Master Thesis
    Reduction Algorithms for the Cryptanalysis of Lattice Based Asymmetrical Cryptosystems
    (Izmir Institute of Technology, 2008) Beyazıt, Mutlu; Koltuksuz, Ahmet Hasan
    The theory of lattices has attracted a great deal of attention in cryptology in recent years. Several cryptosystems are constructed based on the hardness of the lattice problems such as the shortest vector problem and the closest vector problem. The aim of this thesis is to study the most commonly used lattice basis reduction algorithms, namely Lenstra Lenstra Lovasz (LLL) and Block Kolmogorov Zolotarev (BKZ) algorithms, which are utilized to approximately solve the mentioned lattice based problems.Furthermore, the most popular variants of these algorithms in practice are evaluated experimentally by varying the common reduction parameter delta in order to propose some practical assessments about the effect of this parameter on the process of basis reduction.These kind of practical assessments are believed to have non-negligible impact on the theory of lattice reduction, and so the cryptanalysis of lattice cryptosystems, due to thefact that the contemporary nature of the reduction process is mainly controlled by theheuristics.
  • Master Thesis
    Comparison of Different Algorithms for Exploting the Hidden Trends in Data Sources
    (Izmir Institute of Technology, 2003) Özsevim, Emrah; Püskülcü, Halis
    The growth of large-scale transactional databases, time-series databases and other kinds of databases has been giving rise to the development of several efficient algorithms that cope with the computationally expensive task of association rule mining.In this study, different algorithms, Apriori, FP-tree and CHARM, for exploiting the hidden trends such as frequent itemsets, frequent patterns, closed frequent itemsets respectively, were discussed and their performances were evaluated. The perfomances of the algorithms were measured at different support levels, and the algorithms were tested on different data sets (on both synthetic and real data sets). The algorihms were compared according to their, data preparation performances, mining performance, run time performances and knowledge extraction capabilities.The Apriori algorithm is the most prevalent algorithm of association rule mining which makes multiple passes over the database aiming at finding the set of frequent itemsets for each level. The FP-Tree algorithm is a scalable algorithm which finds the crucial information as regards the complete set of prefix paths, conditional pattern bases and frequent patterns by using a compact FP-Tree based mining method. The CHARM is a novel algorithm which brings remarkable improvements over existing association rule mining algorithms by proving the fact that mining the set of closed frequent itemsets is adequate instead of mining the set of all frequent itemsets.Related to our experimental results, we conclude that the Apriori algorithm demonstrates a good performance on sparse data sets. The Fp-tree algorithm extracts less association in comparison to Apriori, however it is completelty a feasable solution that facilitates mining dense data sets at low support levels. On the other hand, the CHARM algorithm is an appropriate algorithm for mining closed frequent itemsets (a substantial portion of frequent itemsets) on both sparse and dense data sets even at low levels of support.
  • Master Thesis
    Heuristic Container Placement Algorithms
    (Izmir Institute of Technology, 2003) Aslan, Burak Galip; Püskülcü, Halis
    With the growth of transportation over sea; defining transportation processes in a better way and finding ways to make transportation processes more effective have become one of the most important research areas of today. Especially in the last quartet of the previous decade, the computers had become much powerful tools with their impressive amount of data processing cababilites. It was imminent that computers had begun taking serious roles in the system development studies. As a result; constructing models for the processes in container terminals and processing the data with the computers create opportunities for the automation of various processes in container terminals. The final step of these studies is the full automation of terminal activities with software packages that combine various functions focused on various processes in a single system.This study is about a project that had been made for a container terminal owned by a special company. During this study; there had been discussions with experts about the subject, and container handling processes in the terminal had been analyzed in order to define the main structure of the yard management software to be created.This study focuses on the container handling activities over the yard space so as to create a basis for a computer system that will take part in the decisions during the container operations. Object oriented analysis and design methods are used for the definition of the system that will help the decisions in the yard operations. The optimization methodology that will be the core of the container placement decisions is based on using different placement patterns and placement algorithms for different conditions. These placement patterns and algorithms are constructed due to the container handling machinery that was being used in the terminal that this study has been made for.