Browsing by Subject "System analysis."

Now showing 1 - 13 of 13

Open Access
Algorithms for the survivable telecommunications network design problem under dedicated protection
(2010) Damcı, Pelin
This thesis presents algorithms to solve a survivable network design problem arising in telecommunications networks. As a design problem, we seek to find 2-edge disjoint paths between every potential origin destination pair such that the fixed costs of installing edges and the routing costs are jointly minimized. Despite the fact that the survivable network design literature is vast, the particular problem at hand incorporating fixed and variable edge costs as well as different cost structures on the two paths has not been studied. Initially, an IP model addressing the proposed problem is developed. In order to solve problems of higher dimensions, different heuristic algorithms are designed and results of a computational study on a large bed of problem instances are reported.
Open Access
Analysis of the daily replenishment information system of an international company: a case study
(1997) Yelbaşi, Ahu
In this thesis, an implementation of Information Systems Analysis is described. As an implementation framework, the Supply & Distribution Department in the Turkish Branch of an international company is used. An analysis of the present information flow of the Daily Replenishment Information System is conducted. Recommendations to improve the existing system is developed.,
Open Access
Analysis of two types of cyclic biological system models with time delays
(2011) Ahsen, Mehmet Eren
In this thesis, we perform the stability analysis of two types of cyclic biological processes involving time delays. We analyze the genetic regulatory network having nonlinearities with negative Schwarzian derivatives. Using preliminary results on Schwarzian derivatives, we present necessary conditions implying the global stability and existence of periodic solutions regarding the genetic regulatory network. We also analyze homogenous genetic regulatory network and prove some stability conditions which only depend on the parameters of the nonlinearity function. In the thesis, we also perform a local stability analysis of a dynamical model of erythropoiesis which is another type of cyclic system involving time delay. We prove that the system has a unique fixed point which is locally stable if the time delay is less than a certain critical value, which is analytically computed from the parameters of the model. By the help of simulations, existence of periodic solutions are shown for delays greater than this critical value.
Open Access
Application of Gauss-Seidel method and singular value decomposition techniques to recursive least squares algorithm
(1991) Malaş, Atilla
System identification algorithms are utilized in many practical and theoretical applications such as parameter estimation of sj'stems, adaptive control and signal processing . Least squares algorithm is one of the most popular algorithms in system identification, but it has some drawbacks such as large time consumption and small convergence rates. In this thesis, Gauss-Seidel method is implemented on recursive least squares algorithm and convergence behaviors of the resultant algorithms are analyzed. .Also in standard recursive least squares algorithm the excitation of modes are monitored using data matrices and this algorithm is accordingly altered. A parallel scheme is proposed in this analysis for efficient computation of the modes. The simulation results are also presented.
Open Access
The 'converge' vs, 'fragmentation' dilemma in metaphoric analysis of organizations
(1996) Keskin, Ayşe Müjde
Eight different organizational studies were performed on ANFA, Ankara Fair Limited Company through the lenses of Morgan’s( 1986) metaphors in 1993 before the municipality elections that changed the political party in charge of the municipality. These eight organizational studies were done through eight different metaphors which were introduced in Gareth Morgan’s book, “Images of Organizations”. These were Organizations As ‘Machines’, ‘Organisms’, ‘Brain’, ‘Culture’, ‘Political Systems’, ‘Psychic Prisons’, ‘Flux & Transformation’ and ‘Instruments of Domination’. The metaphoric organizational analysis are considered part of the postmodern approach. According to this approach, the organizational analysis should be able to find the ‘instabilities’ of the ‘formal’ reality of the organization to uncover the ‘difference’ -- multi-dimensions of the organizational reality . The eight metaphoric studies were designed as an experiment. The purpose of this study to test this postmodern proposition of a multifaceted representational reality.
Open Access
Design and software implementation of library functions for electronic circuit simulation
(1994) Yazgan, Mustafa Nazım
In this thesis, the software implementation of “SIMLIB” , a library of electronic circuit simulation, is described. The building blocks of a circuit simulator, namely, input parser, types of analyses, methods and matrix solvers are discussed. The algorithms and some special techniques employed in this library, as well as ways of modifying the program are explained. SIMLIB has become a good environment for the researchers to try гınd develop new ideas on circuit simulation.
Open Access
Exact and approximate decoupling and noninteracting control problems
(1989) Akar, Nail
In this thesis, we consider “exact” and “approximate” versions of the disturbance decoupling problem and the noninteracting control problem for linear, time-invariant systems. In the exact versions of these problems, we obtain necessary and sufficient conditions for the existence of an internally stabilizing dynamic output feedback controller such that prespecified interactions between certain sets of inputs and certain sets of outputs are annihilated in the closed-loop system. In the approximate version of these problems we require these interactions to be quenched in the ‘Hoo sense, up to any degree of accuracy. The solvability of the noninteracting control problems are shown to be equivalent to the existence of a common solution to two linear matrix equations over a principal ideal domain. A common solution to these equations exists if and only if the equations each have a solution and a bilateral matrix equation is solvable. This yields a system theoretical interpretation for the solvability of the original noninteracting control problem.
Open Access
High-gain sampled-data control of interconnected systems
(2002) Altunel, Haluk
Stabilization of interconnected systems using adaptive, decentralized, high-gain, sampled-data controllers is considered. Main applications of high-gain methodology to various systems under modeling uncertainties are reviewed. Then, sampled-data, high-gain and decentralized control techniques are combined to nd a solution to stabilization of interconnected systems, while satisfying the overall synchronization of the whole system. It is shown that overall system can be stabilized in continuous and discrete time domains by applying an adaptation mechanism for perturbations with unknown bounds.
Open Access
Identification of some nonlinear systems by using least-squares support vector machines
(2010) Yavuzer, Mahmut
The well-known Wiener and Hammerstein type nonlinear systems and their various combinations are frequently used both in the modeling and the control of various electrical, physical, biological, chemical, etc... systems. In this thesis we will concentrate on the parametric identification and control of these type of systems. In literature, various identification methods are proposed for the identification of Hammerstein and Wiener type of systems. Recently, Least Squares-Support Vector Machines (LS-SVM) are also applied in the identification of Hammerstein type systems. In the majority of these works, the nonlinear part of Hammerstein system is assumed to be algebraic, i.e. memoryless. In this thesis, by using LS-SVM we propose a method to identify Hammerstein systems where the nonlinear part has a finite memory. For the identification of Wiener type systems, although various methods are also available in the literature, one approach which is proposed in some works would be to use a method for the identification of Hammerstein type systems by changing the roles of input and output. Through some simulations it was observed that this approach may yield poor estimation results. Instead, by using LS-SVM we proposed a novel methodology for the identification of Wiener type systems. We also proposed various modifications of this methodology and utilized it for some control problems associated with Wiener type systems. We also proposed a novel methodology for identification of NARX (Nonlinear Auto-Regressive with eXogenous inputs) systems. We utilize LS-SVM in our methodology and we presented some results which indicate that our methodology may yield better results as compared to the Neural Network approximators and the usual Support Vector Regression (SVR) formulations. We also extended our methodology to the identification of Wiener-Hammerstein type systems. In many applications the orders of the filter, which represents the linear part of the Wiener and Hammerstein systems, are assumed to be known. Based on LS-SVR, we proposed a methodology to estimate true orders
Open Access
An implementation of structured systems analysis to an information technology company
(1996) Alparslan, Korhan
Systems Analysis is the process of analyzing an organization with the ultimate objective of modifying and improving it. It is a way of solving problems existing in organizations. Structured Analysis, with the aid of visual capabilities, is the most commonly applied technique of implementing systems analysis. The two major components of structured analysis are Data Flow Diagrams(DFDs) and Data Dictionary. Wide-spread usage of Computer-Aided Software Engineering(CASE) tools that support systems analysis and design made the structured analysis process easier to manage and control. This study aims to apply structured analysis methodology to a Turkish company that operates in the information technology industry. Context diagram which is level 0 DFD is developed initially. Then the level 1 and level 2 DFDs are produced. The DFDs display the processes of each department and data flow between, in and out of departments. Each process that exists in the level 2 DFDs is explained and the data dictionary is provided in the appendices. The study concludes with a summary of recommendations that can be implemented for the improvement of the organization work flow.
Open Access
Output regulation for all-pole and minimum phase LTI
(2010) Saldı, Naci
In this thesis, the problem of enabling the output of a system to track the reference signals and reject the disturbances created by the same exogenous system is considered. This problem is widely known as Output Regulation Problem. Firstly, we propose a method for all-pole LTI systems by using relative degree property and then we apply the same method for minimum phase LTI systems along with some modifications. In order to obtain controllers for a minimum phase LTI case, the system is converted into an all-pole system by employing the inverse system as the first part of the controller. Then using the method that we used in all-pole cases, we obtain the second part of the controller. Combining these two controllers gives us an overall controller which solves the output regulation problem. This method for LTI systems is then extended to all-pole and minimum phase LTV systems. However, in order to apply the same methodology we have to make some assumptions on LTV systems. For minimum phase cases, the normal form is obtained by applying certain Lyapunov transformations and then minimum phaseness is defined in accordance with the normal form. Furthermore we show that, similar to minimum phase LTI cases, pole / zero cancelations occur between the inverse system and the original system in minimum phase LTV cases. The method that we develop depends on analytical calculation of the controller and gives a certain degree of freedom to change the transient behavior of the system by only changing some controller parameters.
Open Access
Ripple-free deadbeat control of sampled-data systems
(1990) Mumcuoğlu, Erkan Ünal
In this thesis, we consider the ripple-free deadbeat control problem for linear, multivariable sampled-data systems represented by state-space models. Existing results concerning the deadbeat/ripple-free deadbeat regulation and tracking problems are based on controller configurations of either constant state-feedback or discrete dynamic output feedback. In the thesis, the problem is analyzed for two new sampled-data controllers, namely, generalized sampled-data hold functions and multirate-output controllers. Some necessary and sufficient solvability conditions for the problem are stated by theorems in time-domain and frequency domain in terms of the open-loop system parameters. Several special cases are also considered as corollaries.
Open Access
Structural analysis of pole assignment and stabilization in dynamic systems
(1989) Şefik, Ayla
Motivated by the need for qualitative investigation of general system properties such as controllability, obser\^bility, existence of fixed modes, etc. as the complement of the quantitative approach in analysis, especially of large-scale systems, the problems of pole assignability and stabilizability are considered from the structural point of view. The study is based on the definition of a generic property as a property that holds for almost all values of the nonzero system parameters. Structured matrices and digraphs are used for system description. Both problems are first formulated in an algebraic setting and then translated to a structural framework by means of several graph-theoretic results which give sufficient conditions for solvability, in terms of the existence of particular cycle families in the digraph. Following a similar approach, a graphical investigation of structural observability is presented. Lastly, genericity of several results are reconsidered in the light of these graphical characterizations.