Real lefschetz fibrations

Salepci, Nermin
In this thesis, we present real Lefschetz fibrations. We first study real Lefschetz fibrations around a real singular fiber. We obtain a classification of real Lefschetz fibrations around a real singular fiber by a study of monodromy properties of real Lefschetz fibrations. Using this classification, we obtain some invariants, called real Lefschetz chains, of real Lefschetz fibrations which admit only real critical values. We show that in case the fiber genus is greater then 1, the real Lefschetz chains are complete invariants of directed real Lefschetz fibrations with only real critical values. If the genus is 1, we obtain complete invariants by decorating real Lefschetz chains. For elliptic Lefschetz fibrations we define a combinatorial object which we call necklace diagrams. Using necklace diagrams we obtain a classification of directed elliptic real Lefschetz fibrations which admit a real section and which have only real critical values. We obtain 25 real Lefschetz fibrations which admit a real section and which have 12 critical values all of which are real. We show that among 25 real Lefschetz fibrations, 8 of them are not algebraic. Moreover, using necklace diagrams we show the existence of real elliptic Lefschetz fibrations which can not be written as the fiber sum of two real elliptic Lefschetz fibrations. We define refined necklace diagrams for real elliptic Lefschetz fibrations without a real section and show that refined necklace diagrams classify real elliptic Lefschetz fibrations which have only real critical values.


Systems thinking skills of preschool children in early childhood education contexts of Turkey and Germany
Feriver Gezer, Şebnem; Olgan, Refika; Teksöz, Gaye; Department of Early Childhood Education (2018)
The goal of this thesis is two-fold. The first goal is to conceptualize nature of the systems thinking skills of 4- to 6-year-old preschool children. Accordingly, an individual story reading and interview session was realized with 52 Turkish and German children. Then the nature of the children’s systems thinking skills were conceptualized by making use of a developmental rubric which was created as part of this study. The second goal of this study is to explore potential educational contextual key variables...
Electromagnetic compatibility of electric power quality monitor according to EN 61326 standard
Yaman, Özgür; Ermiş, Muammer; Department of Electrical and Electronics Engineering (2007)
In this thesis; Electromagnetic Compatibility (EMC) of Electric Power Quality Monitor developed within the scope of National Power Quality Project has been investigated according to EN 61326 standard. Both immunity and emission tests have been carried out in EMC laboratories of ELDAS and ASELSAN for the device under test. Necessary counter measures such as using electromagnetic interference (EMI) filters and transient voltage suppressors, shielding the case of device with EMI protective materials have been ...
Second-order scalar-tensor field theories
Şahin, Ertan Sinan; Sarıoğlu, Bahtiyar Özgür; Department of Physics (2017)
We review Horndeski’s scalar-tensor theory in this thesis. Partial differential equations that are satisfied by the Lagrangian limit its most general form. Demanding second-order field equations both for the metric and the scalar field, and choosing a four-dimensional spacetime also put restrictions on the most general form of the Lagrangian. Besides, by using similar techniques, in a four-dimensional spacetime, we find the most general form of the second-order Euler-Lagrange equations that are obtained fro...
A switch mode power supply for producing half wave sine output
Kaya, İbrahim; Ertan, Hulusi Bülent; Department of Electrical and Electronics Engineering (2008)
In this thesis; analysis, design and implementation of a DC-DC converter with active clamp forward topology is presented. The main objective of this thesis is generating a rectified sinusoidal voltage at the output of the converter. This is accomplished by changing the reference signal of the converter. The converter output is applied to an inverter circuit in order to obtain sinusoidal waveform. The zero crossing points of the converter is detected and the inverter drive signals are generated in order to o...
Robust quality metrics for assessing multimodal data
Konuk, Barış; Akar, Gözde; Department of Electrical and Electronics Engineering (2015)
In this thesis work; a novel, robust, objective, no-reference video quality assessment (VQA) metric, namely Spatio-Temporal Network aware Video Quality Metric (STNVQM), has been proposed for estimating perceived video quality under compression and transmission distortions. STN-VQM uses parameters reflecting the spatiotemporal characteristics of the video such as spatial complexity and motion. STN-VQM also utilizes parameters representing distortions due to compression and transmission such as bit rate and p...
Citation Formats
N. Salepci, “Real lefschetz fibrations,” Ph.D. - Doctoral Program, Middle East Technical University, 2007.