Özlem Özgün

Dear students and friends, welcome to my webpage.

I am a Professor of Electrical & Electronics Engineering Department @ Hacettepe University, Ankara, Turkey. My main research and teaching area is Electromagnetics. I invite you to surf through my webpage to learn the details about my activites. Enjoy !

Resume

EDUCATION

Ph.D (2007): Middle East Technical University, Dept. of Electrical and Electronics Engineering, Ankara, Turkey

M.Sc (2001): Bilkent University, Dept. of Electrical and Electronics Engineering, Ankara, Turkey

B.Sc (1998): Bilkent University, Dept. of Electrical and Electronics Engineering, Ankara, Turkey

EXPERIENCE

2018 - present: Professor, Hacettepe University, Dept. of Electrical and Electronics Engineering, Ankara, Turkey

2015 - 2018: Associate Professor, Hacettepe University, Dept. of Electrical and Electronics Engineering, Ankara, Turkey

2012-2015: Associate Professor, TED University, Dept. of Electrical and Electronics Engineering, Ankara, Turkey

2008-2012: Assistant Professor, Middle East Technical University - Northern Cyprus Campus, Dept. of Electrical and Electronics Engineering, Cyprus.

2007-2008: Postdoctoral Research Fellow, Penn State University , Electromagnetic Communication LabUniversity Park, PA 16802

2004-2005: Expert System Engineer, ASELSAN Inc., Microwave and System Technologies (MST) Division, Ankara

2000-2004: Research Scientist, TÜBİTAK - Iltaren, Ankara

1998-2000: Teaching Assistant, Bilkent University, Department of Electrical and Electronics Engineering, Ankara

HONORS

2014: Best paper award (The Chamber of Electrical Engineers (EMO) journal) Click

2009: Prof. Dr. Leopold B. Felsen Award for Excellence in Electromagnetics

2007: Best thesis award (METU Graduate School of Natural and Applied Sciences)

2007-2008: TÜBİTAK-BİDEB 2219 postdoctoral research grant

2006: Best presentation award (URSI-Türkiye 2006 3rd Scientific Congress, Hacettepe Univ, Ankara)

1998-2001: Full graduate scholarship, Bilkent University, Department of Electrical and Electronics Engineering

1993-1998: Full under-graduate scholarship, Bilkent University, Department of Electrical and Electronics Engineering

1993: Ranked 94th in the nation-wide University Entrance Exam (OYS)

1993: Offer of scholarship for undergraduate study in foreign countries (Turkish prime minister) (not used)

PROFESSIONAL SERVICE

2005-present: Senior member of IEEE (Institute of Electrical and Electronics Engineers)

2014-present: Secretary of Steering Committee of URSI-Türkiye (International Union of Radio Science)

2015-present: Professional service at Hacettepe University

  • Department Vice Chair (Dept. of Electrical and Electronics Engineering) (2017-...)
  • Member of Faculty Administration Committee (2017-2018)

2012-2015: Professional service at TED University

  • Acting Department Head (Dept. of Electrical and Electronics Engineering)
  • Member of University Senate
  • Member of Faculty Committee
  • Member of Faculty Administration Committee
  • Head/Member of Commission of Library
  • Member of Commission of Scholarship
  • Member of Commission of Quality Assurance

2014: Special Session Organizer and Chair/Co-chair in the 5th International Conference on Metamaterials, Photonic Crystals and Plasmonics (META'14), Singapore, 20 – 23 May 2014. Title of the session: Numerical modeling techniques for metamaterials

2013: Special Session Organizer and Chair/Co-chair in the 4th International Conference on Metamaterials, Photonic Crystals and Plasmonics (META'13), Sharjah, UAE, 18 – 22 March 2013. Title of the session: Novel applications of transformation electromagnetics

2013: Member of local organizing committee in "6th URSI-Türkiye Scientific Congress", and "12th edition of the Mediterranean Microwave Symposium (MMS-2012)", Doğuş University, Sept. 2-5, 2012.

2012: Local organizing committee chair and co-chair, respectively, in "5th URSI-Türkiye Scientific Congress", and "10th edition of the Mediterranean Microwave Symposium (MMS-2010)", METU-NCC, August 25-27, 2010.

2006-present: Reviewer for several international journals

home

Publications

BOOK
Author(s) Title Publisher Year
  • Image
  • O.Ozgun, M.Kuzuoglu MATLAB-based Finite Element Programming in Electromagnetic Modeling CRC Press (ISBN: 9781498784078) 2018

     

    BOOK CHAPTER
    No Author(s) Title Publisher Year
    1 O.Ozgun, M.Kuzuoglu Transformation optics-based computational materials for stochastic electromagnetics Chapter 9 in Advanced Engineering Materials and Modeling, pp: 241-286, Editor: A. Tiwari, Wiley-Scrivener (ISBN: 9781119242468) 2016
    2 O.Ozgun, M.Kuzuoglu Form-invariance of Maxwell's Equations in Coordinate Transformations: Metamaterials and Numerical Models Chapter 3 in Metamaterials: Classes, Properties and Applications, pp: 87-136, Editor: Ethan J. Tremblay, Nova Science Publishers (ISBN: 978-1-61668-958-2) 2010

     

    INTERNATIONAL JOURNAL PAPERS (SCI / SCIE)
    No Author(s) Title Journal Year Index
    46 O.Ozgun, M.Kuzuoglu A Domain Decomposition Finite Element Method for Modeling Electromagnetic Scattering from Rough Sea Surfaces with Emphasis on Near-Forward Scattering

    IEEE Transactions on Antennas and Propagation,

    vol. 67, vol. 1, pp. 335-345

    2019 SCI
    45 O.Ozgun, M.Kuzuoglu Coordinate Transformation Aided Finite Element Method for Contour Detection of Breast Tumors in Microwave Imaging

    International Journal for Numerical Methods in Biomedical Engineering,

    e3124, pp. 1-17

    2018 SCIE
    44 O.Ozgun Modeling of Diffraction Effects in Urban Radiowave Propagation

    ACES - Applied Computational Electromagnetics Society Journal,

    vol. 32, no. 7, pp. 593-599

    2017 SCIE
    43 O.Ozgun, L.Sevgi Finite Element Modeling of Fringe Waves in Wedge Diffraction Problem

    IEEE Antennas and Wireless Propagation Letters,

    vol. 16, pp. 369-372

    2017 SCIE
    42 O.Ozgun, M.Kuzuoglu Remesh-free Shape Optimization by Transformation Optics

    IEEE Transactions on Antennas and Propagation,

    vol. 64, no. 12, pp. 5479-5482

    2016 SCI
    41 O.Ozgun New Software Tool GO+UTD for Visualization of Wave Propagation

    IEEE Antennas and Propagation Magazine,

    vol. 58, no. 3, pp. 91–103

    Program download

    2016 SCIE
    40 O.Ozgun, M.Kuzuoglu Implementation of coordinate transformations in periodic finite-element method for modeling rough surface scattering problems

    International Journal of RF and Microwave Computer-Aided Engineering,

    vol. 26, no. 4, pp. 322–329

    2016 SCIE
    39 O.Ozgun, M.Kuzuoglu Monte Carlo simulations of Helmholtz scattering from randomly positioned array of scatterers by utilizing coordinate transformations in finite element method

    Wave Motion,

    vol. 56, pp. 165-182

    2015 SCI
    38 O.Ozgun, L.Sevgi Double-tip Diffraction Modeling: 2D Numerical Models vs. High Frequency Asymptotics

    IEEE Transactions on Antennas and Propagation,

    vol. 63, no. 6, pp. 2686 - 2693

    2015 SCI
    37 O.Ozgun, L.Sevgi VectGUI: A MATLAB-Based Simulation Tool

    IEEE Antennas and Propagation Magazine,

    vol. 57, no. 3, pp. 113-118

    Program download

    2015 SCIE
    36 O.Ozgun, M.Kuzuoglu Cartesian Grid Mapper: Transformation media for modeling arbitrary curved boundaries with Cartesian grids

    IEEE Antennas and Wireless Propagation Letters,

    special cluster on "Transformation Electromagnetics",

    vol. 13, pp. 1771-1774

    2014 SCIE
    35 O.Ozgun, M.Kuzuoglu Approximation of transformation media-based reshaping action by genetic optimization

    Applied Physics A - Material Science and Processing,

    vol. 117, no. 2, pp. 597-604

    2014 SCI
    34 M.Kuzuoglu, O.Ozgun Combining perturbation theory and transformation electromagnetics for finite element solution of Helmholtz-type scattering problems

    Journal of Computational Physics,

    vol. 274, pp. 883-897

    2014 SCI
    33 O.Ozgun, M.Kuzuoglu A coordinate transformation approach for efficient repeated solution of Helmholtz equation pertaining to obstacle scattering by shape deformations

    Computer Physics Communications,

    vol. 185, no. 6, pp. 1616-1627

    2014 SCI
    32 O.Ozgun, G.Apaydin, M.Kuzuoglu, L.Sevgi Comments on “propagation modeling over irregular terrain by the improved two-way parabolic equation method”

    IEEE Transactions on Antennas and Propagation,

    vol. 62, no. 7, pp. 3894

    2014 SCI
    31 O.Ozgun, M.Kuzuoglu A Transformation Media Based Approach for Efficient Monte Carlo Analysis of Scattering from Rough Surfaces with Objects

    IEEE Transactions on Antennas and Propagation,

    vol. 61, no. 3, pp. 1352 - 1362

    2013 SCI
    30 O.Ozgun, M.Kuzuoglu Transformation Electromagnetics Based Analysis of Waveguides with Random Rough or Periodic Grooved Surfaces

    IEEE Transactions on Microwave Theory and Techniques,

    vol. 61, no. 2, pp. 709 - 719

    2013 SCI
    29 O.Ozgun, M.Kuzuoglu Monte Carlo Analysis of Ridged Waveguides with Transformation Media

    International Journal of RF and Microwave Computer-Aided Engineering,

    special issue on "Modeling and Simulation Challenges in Microwave Engineering",

    vol. 23, no. 4, pp. 476 – 481

    2013 SCIE
    28 O.Ozgun, M.Kuzuoglu Software Metamaterials: Transformation Media Based Multiscale Techniques for Computational Electromagnetics

    Journal of Computational Physics,

    vol. 236, pp. 203-219

    2013 SCI
    27 O.Ozgun, R.Mittra, M.Kuzuoglu Comments on "ParAFEMCap: A Parallel Adaptive Finite-Element Method for 3-D VLSI Interconnect Capacitance Extraction"

    IEEE Transactions on Microwave Theory and Techniques,

    vol. 60, no. 6, pp. 1744-1745

    2012 SCI
    26 O.Ozgun, M.Kuzuoglu Transformation-based Metamaterials to Eliminate the Staircasing Error in the Finite Difference Time Domain Method

    Int. Journal of RF and Microwave Computer-Aided Engineering,

    special Issue on "Metamaterials: RF and Microwave Applications",

    vol. 22, no. 4, pp. 530-540

    2012 SCIE
    25 O.Ozgun, L.Sevgi Comparative Study of Analytical and Numerical Techniques in Modeling Electromagnetic Scattering from Single and Double Knife-Edge in 2D Ground Wave Propagation Problems

    ACES - Applied Computational Electromagnetics Society Journal,

    vol. 27, no. 5, pp. 376-388

    2012 SCIE
    24 O.Ozgun, M.Kuzuoglu Monte Carlo-based Characteristic Basis Finite Element Method (MC-CBFEM) for Numerical Analysis of Scattering from Objects on/above Rough Sea Surfaces

    IEEE Transactions on GeoScience and Remote Sensing,

    vol. 50, no. 3, pp. 769-783

    2012 SCI
    23 O.Ozgun, G.Apaydin, M.Kuzuoglu, L.Sevgi

    PETOOL: MATLAB-based One-Way and Two-Way Split-Step Parabolic Equation Tool for Radiowave Propagation over Variable Terrain

    Computer Physics Communications,

    vol. 182, no. 12, pp. 2638–2654

    Program download

    2011 SCI
    22 G.Apaydin, O.Ozgun, M.Kuzuoglu, L.Sevgi A Novel Two-Way Finite-Element Parabolic Equation (FEMPE) Groundwave Propagation Tool: Tests with Canonical Structures and Calibration

    IEEE Transactions on GeoScience and Remote Sensing,

    vol. 49, no. 8, pp. 2887 - 2899

    2011 SCI
    21 O.Ozgun, M.Kuzuoglu Form Invariance of Maxwell's Equations: The Pathway to Novel Metamaterial Specifications for Electromagnetic Reshaping

    IEEE Antennas and Propagation Magazine,

    vol. 52, no. 3, pp. 51-65

    2010 SCIE
    20 O.Ozgun, M.Kuzuoglu Domain Compression via Anisotropic Metamaterials designed by Coordinate Transformations

    Journal of Computational Physics,

    vol. 229, no. 3, pp. 921-932

    2010 SCI
    19 O.Ozgun, R.Mittra, M.Kuzuoglu PO-based Characteristic Basis Finite Element Method (CBFEM-PO) - A Parallel, Iteration-free Domain Decomposition Algorithm using Perfectly Matched Layers for Large-scale Electromagnetic Scattering Problems

    Microwave and Optical Technology Letters,

    vol.52, no. 5, pp. 1053-1060

    2010 SCIE
    18 O.Ozgun, R.Mittra, M.Kuzuoglu General Purpose Characteristic Basis Finite Element Method (CBFEM) for Multi-Scale Electrostatic and Electromagnetic Problems

    Electromagnetics,

    special issue of "9th International Workshop on Finite Elements for Microwave Engineering",

    vol. 30, no. 1&2, pp. 205-221

    2010 SCI
    17 O.Ozgun, M.Kuzuoglu Iterative Leap-Field Domain Decomposition Method - A Domain Decomposition Finite Element Algorithm for 3D Electromagnetic Boundary Value Problems

    IET Microwaves, Antennas & Propagation,

    vol. 4, no. 4, pp. 543-552

    2010 SCI
    16 O.Ozgun, R.Mittra, M.Kuzuoglu Multi-Level Characteristic Basis Finite Element Method (ML-CBFEM) - An Efficient Version of A Parallel, Non-iterative Domain Decomposition Algorithm for Direct Solution of Large-scale Electromagnetic Problems

    IEEE Transactions on Antennas and Propagation,

    vol. 57, no. 10, pp. 3381-3387

    2009 SCI
    15 O.Ozgun, R.Mittra, M.Kuzuoglu Parallelized Characteristic Basis Finite Element Method (CBFEM-MPI) - A Non-iterative Domain Decomposition Algorithm for Electromagnetic Scattering Problems

    Journal of Computational Physics,

    vol. 228, no. 6, pp. 2225-2238

    2009 SCI
    14 O.Ozgun, M.Kuzuoglu Form-invariance of Maxwell's Equations in Waveguide Cross-section Transformations

    Electromagnetics,

    vol.29, no. 4, pp. 353-376

    2009 SCI
    13 O.Ozgun, R.Mittra, M.Kuzuoglu CBFEM-MPI: A Parallelized Version of Characteristic Basis Finite Element Method for Extraction of 3D Interconnect Capacitances

    IEEE Transactions on Advanced Packaging,

    vol. 32, no.1, pp. 164-174

    2009 SCI
    12 O.Ozgun Recursive Two-way Parabolic Equation Approach for Modeling Terrain Effects in Tropospheric Propagation

    IEEE Transactions on Antennas and Propagation,

    vol. 57, no. 9, pp. 2706-2714

    2009 SCI
    11 O.Ozgun, M.Kuzuoglu Efficient Finite Element Solution of Low-Frequency Scattering Problems via Anisotropic Metamaterial Layers

    Microwave and Optical Technology Letters,

    vol. 50, no. 3, pp. 639-646

    2008 SCIE
    10 O.Ozgun, M.Kuzuoglu Finite Element Analysis of Electromagnetic Wave Problems via Iterative Leap-Field Domain Decomposition Method

    Journal of Electromagnetic Waves and Applications,

    vol. 22, no. 2, pp. 251-266

    2008 SCIE
    9 O.Ozgun, M.Kuzuoglu Recent Advances in Perfectly Matched Layers in Finite Element Applications

    The Turkish Journal of Electrical Engineering & Computer Sciences,

    special issue on "From Engineering Electromagnetics towards Electromagnetic Engineering: Issues, Challenges and Applications - Dedicated to the 75th birthday of Prof. Dr. Raj Mittra",

    vol. 16, no. 1, pp. 57-66

    2008 SCIE
    8 O.Ozgun, M.Kuzuoglu Utilization of Anisotropic Metamaterial Layers in Waveguide Miniaturization and Transitions

    IEEE Microwave and Wireless Components Letters,

    vol. 17, no. 11, pp. 754-756

    2007 SCI
    7 O.Ozgun, M.Kuzuoglu Electromagnetic Metamorphosis: Reshaping Scatterers via Conformal Anisotropic Metamaterial Coatings

    Microwave and Optical Technology Letters,

    vol. 49, no. 10, pp. 2386-2392

    2007 SCIE
    6 O.Ozgun, M.Kuzuoglu Forward-Backward Domain Decomposition Method for Finite Element Solution of Boundary Value Problems

    Microwave and Optical Technology Letters,

    vol. 49, no. 10, pp. 2582-2590

    2007 SCIE
    5 O.Ozgun, M.Kuzuoglu Near-field Performance Analysis of Locally-conformal Perfectly Matched Absorbers via Monte Carlo Simulations

    Journal of Computational Physics,

    vol. 227, Issue 2, pp. 1225-1245

    2007 SCI
    4 O.Ozgun, M.Kuzuoglu Multi-center Perfectly Matched Layer Implementation for Finite Element Mesh Truncation

    Microwave and Optical Technology Letters,

    vol. 49, no. 4, pp. 827-832

    2007 SCIE
    3 O.Ozgun, M.Kuzuoglu Non-Maxwellian Locally-conformal PML Absorbers for Finite Element Mesh Truncation

    IEEE Transactions on Antennas and Propagation,

    vol. 55, no. 3, pp. 931-937

    2007 SCI
    2 O.Ozgun, M.Kuzuoglu Locally-Conformal Perfectly Matched Layer Implementation for Finite Element Mesh Truncation

    Microwave and Optical Technology Letters,

    vol. 48, no. 9, pp. 1836-1839

    2006 SCI
    1 O.Ozgun, S.Mutlu, M.I.Aksun, L.Alatan Design of Dual-Frequency Probe-Fed Microstrip Antennas with Genetic Optimization Algorithm

    IEEE Transactions on Antennas and Propagation,

    vol. 51, no: 8, pp. 1947-1954

    2003 SCI

     

    PAPERS in OTHER INDEXED INTERNATIONAL JOURNALS
    No Author(s) Title Journal Year
    4 O.Ozgun, M.Kuzuoglu Complex Coordinate Approaches with Applications to Perfectly Matched and Double Negative Layers

    Forum for Electromagnetic Research Methods and Application Technologies (FERMAT),

    vol. 18, article no: 2, pp. 1-12

    2016
    3 O.Ozgun Ozlem Ozgun's Autobiography

    Forum for Electromagnetic Research Methods and Application Technologies (FERMAT),

    vol. 3 (Women in Engineering Corner) (invited)

    2014
    2 O.Ozgun, M.Kuzuoglu Recent Developments in Transformation Optics-aided CEM

    Forum for Electromagnetic Research Methods and Application Technologies (FERMAT),

    vol. 1, paper no: 3, pp. 1-15 (invited paper)

    2014
    1 O.Ozgun, M.Kuzuoglu Numerical Solution of Multi-scale Electromagnetic Boundary Value Problems by Utilizing Transformation-based Metamaterials

    Lecture Notes in Computer Science,

    special issue of "11th International Conference on Computational Science and Its Applications",

    volume 6785/2011, pp. 11-25

    2011

     

    NATIONAL JOURNAL PAPERS
    No Author(s) Title Journal Year
    2 Ö.Özgün Binalar Arası Elektromanyetik Dalga Yayılımının Nümerik Modellenmesi

    EMO Bilimsel Dergi,

    cilt 6, sayı 11, sayfa 25-32

    2016
    1 M.Kuzuoğlu, Ö.Özgün Dönüşümsel Elektromanyetik Yaklaşımı ile Dalgalı Deniz Yüzeyi ve Üzerindeki Cisimlerden Saçılma Probleminin Etkin Monte Carlo Simülasyonu

    EMO Bilimsel Dergi,

    cilt 3, sayı 5, sayfa 41-48

    (Received EMO best paper award. Click)

    2013

     

    INTERNATIONAL REFEREED CONFERENCE PAPERS
    No Author(s) Title Conference Year
    41 G.Y.Altun, O.Ozgun Electromagnetic Propagation Modeling Over Irregular Terrain Using a New Hybrid Method

    The 18th Mediterranean Microwave Symposium (MMS),

    Oct.31-Nov.02, İstanbul, Turkey.

    2018
    40 C.Pay, O.Ozgun A Radar Cross Section Reduction Method Using the Concept of Coordinate Transformation and Isotropic Dielectric Layers

    The 18th Mediterranean Microwave Symposium (MMS),

    Oct.31-Nov.02, İstanbul, Turkey.

    2018
    39 O.Ozgun Advanced finite element analysis for EMC engineering

    The Fourth International EMC Conference,

    Sept. 24-27, Ankara, Turkey.

    2017
    38 O.Ozgun A Comparative Study of Radiowave Propagation Models for Urban and Suburban Paths

    IEEE AP-S Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting,

    July 9-14, San Diego, CA, USA.

    2017
    37 O.Ozgun, M.Kuzuoglu Finite Element Modeling of Anisotropic Half-Space Problems by a Simple Mesh Truncation Scheme

    IEEE AP-S Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting,

    July 9-14, San Diego, CA, USA.

    2017
    36 O.Ozgun, M.Kuzuoglu A Microwave Imaging Model for Biomedical Applications

    IEEE AP-S Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting,

    July 9-14, San Diego, CA, USA.

    2017
    35 M.Kuzuoglu, O.Ozgun A Numerical Model for Investigating the Effect of Rough Surface Parameters on Radar Cross Section Statistics

    IEEE AP-S Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting,

    July 9-14, San Diego, CA, USA.

    2017
    34 O.Ozgun, M.Kuzuoglu Numerical Modeling of Electromagnetic Scattering from Periodic Structures by Transformation Electromagnetics

    10th International Congress on Advanced Electromagnetic Materials in Microwaves and Optics (Metamaterials 2016),

    September 17-22, Crete, Greece.

    2016
    33 M.Kuzuoglu, O.Ozgun A Microwave Imaging Method based on Transformation Electromagnetics

    10th International Congress on Advanced Electromagnetic Materials in Microwaves and Optics (Metamaterials 2016),

    September 17-22, Crete, Greece.

    2016
    32 O.Ozgun, M.Kuzuoglu Stochastic Modeling in Computational Electromagnetics by Coordinate Transformations

    The Third International EMC Conference,

    September 2-4, Istanbul, Turkey.

    2015
    31 O.Ozgun, M.Kuzuoglu Modeling Electromagnetic Scattering from Random Array of Objects by Form Invariance of Maxwell’s Equations

    IEEE AP-S International Symposium on Antennas and Propagation and USNC/URSI North American Radio Science Meeting,

    July 19-25, Vancouver, BC, Canada.

    2015
    30 M.Kuzuoglu, O.Ozgun A Hybrid Perturbational and Transformational Electromagnetics Approach for Modeling Rough Surface Scattering Problems

    IEEE AP-S International Symposium on Antennas and Propagation and USNC/URSI North American Radio Science Meeting,

    July 19-25, Vancouver, BC, Canada.

    2015
    29 O.Ozgun, L.Sevgi Finite Element Modeling of Double-tip Diffraction

    IEEE AP-S International Symposium on Antennas and Propagation and USNC/URSI North American Radio Science Meeting,

    July 19-25, Vancouver, BC, Canada.

    2015
    28 O.Ozgun, G.Apaydin, M.Kuzuoglu, L.Sevgi Parabolic Equation Toolbox for Radio Wave Propagation

    IEEE AP-S International Symposium on Antennas and Propagation and USNC/URSI North American Radio Science Meeting,

    July 19-25, Vancouver, BC, Canada.

    2015
    27 O.Ozgun, M.Kuzuoglu Modeling and Predicting Surface Roughness via Transformation Optics

    8th International Congress on Advanced Electromagnetic Materials in Microwaves and Optics (Metamaterials 2014),

    August 25-30, Copenhagen, Denmark.

    2014
    26 O.Ozgun, M.Kuzuoglu Approximation of Transformation Media-based Reshaping Action by Genetic Optimization

    5th International Conference on Metamaterials, Photonic Crystals and Plasmonics (META'14),

    May 20 – 23, Singapore.

    2014
    25 O.Ozgun, M.Kuzuoglu Transformation Electromagnetics for Efficient Solution of Rough Surface Scattering Problems by Finite Methods

    4th International Conference on Metamaterials, Photonic Crystals and Plasmonics (META'13),

    March 18 – 22, Sharjah, UAE.

    2013
    24 O.Ozgun, M.Kuzuoglu Transformation-based Metamaterials for Enhancing the Ability of Computational Methods in Electromagnetics

    3rd International Conference on Metamaterials, Photonic Crystals and Plasmonics (META’12),

    April 19-22, Paris, France.

    2012
    23 O.Ozgun, M.Kuzuoglu Statistical Transformation Electromagnetics for the Analysis of Waveguide Problems

    Mediterranean Microwave Symposium MMS,

    Sept. 2-5, Istanbul, Turkey.

    2012
    22 O.Ozgun, M.Kuzuoglu Designing Transformation-based Metamaterials for Numerical Modeling of Low Frequency Electromagnetic Scattering

    PIERS Progress In Electromagnetics Research Symposium,

    August 19-23, Moscow, Russia.

    2012
    21 M.Kuzuoglu, O.Ozgun Reduction of the Staircasing Error in Finite Methods by Using Transformation Media

    PIERS Progress In Electromagnetics Research Symposium,

    August 19-23, Moscow, Russia.

    2012
    20 O.Ozgun, M.Kuzuoglu Numerical Solution of Multi-scale Electromagnetic Boundary Value Problems by Utilizing Transformation-based Metamaterials

    ICCSA 2011 - The 11th International Conference on Computational Science and Its Applications,

    June 20-23, University of Cantabria, Santander, Spain.

    2011
    19 M.Kuzuoglu, O.Ozgun Transformation Media for Finite Element Solution of Multi-scale Electromagnetic Boundary Value Problems

    URSIGASS 2011 - XXX General Assembly and Scientific Symp. of the International Union of Radio Science,

    August 13-20, Istanbul, Turkey.

    2011
    18 R.Mittra, R.J.Bringuier, C.Pelletti, K.Panayappan, O.Ozgun, A.Monorchio On the Hybridization of Dipole Moment (DM) and Finite Methods for Efficient Solution of Multiscale Problems

    5th European Conference on Antennas and Propagation (EUCAP),

    pp. 3368 - 3369, April 11-15, Rome, Italy.

    2011
    17 O.Ozgun, G.Apaydin, M.Kuzuoglu, L.Sevgi Two-way Split-Step Parabolic Equation Algorithm for Tropospheric Propagation: Tests and Comparisons

    The 10th Mediterranean Microwave Symposium MMS,

    August 25-27, Middle East Technical University - Northern Cyprus Campus.

    2010
    16 O.Ozgun, R.Mittra, M.Kuzuoglu Solving Multiscale EM Problems Using A New Approach To Hybridizing the Finite Element Method

    The 10th International Workshop on Finite Elements for Microwave Engineering,

    October 12-13, New England, USA.

    2010
    15 O.Ozgun, R.Mittra, M.Kuzuoglu A Multilevel Characteristic Basis Finite Element Method for Efficient Solution of Large EM Problems

    The 10th International Workshop on Finite Elements for Microwave Engineering,

    October 12-13, New England, USA.

    2010
    14 O.Ozgun, R.Mittra, M.Kuzuoglu Finite Element / Dipole Moment Method for Efficient Solution of Multiscale Electromagnetic Problems

    IEEE AP-S International Symposium on Antennas and Propagation and USNC/URSI National Radio Science Meeting,

    July 11 - 17, Sheraton Toronto Centre Hotel, ON, Canada.

    2010
    13 O.Ozgun, R.Mittra, M.Kuzuoglu Solution of Large Scattering Problems using a Multilevel Scheme in the context of Characteristic Basis Finite Element Method

    IEEE AP-S International Symposium on Antennas and Propagation and USNC/URSI National Radio Science Meeting,

    July 11 - 17, Sheraton Toronto Centre Hotel, ON, Canada.

    2010
    12 M.Kuzuoglu, O.Ozgun Transformation Media for Efficient Numerical Modeling of Finite Methods

    IEEE AP-S International Symposium on Antennas and Propagation and USNC/URSI National Radio Science Meeting,

    July 11 - 17, Sheraton Toronto Centre Hotel, ON, Canada.

    2010
    11 O.Ozgun, G.Apaydin, M.Kuzuoglu, L.Sevgi Two-way Fourier Split Step Algorithm over Variable Terrain with Narrow and Wide Angle Propagators

    IEEE AP-S International Symposium on Antennas and Propagation and USNC/URSI National Radio Science Meeting,

    July 11 - 17, Sheraton Toronto Centre Hotel, ON, Canada.

    2010
    10 G.Apaydin, O.Ozgun, M.Kuzuoglu, L.Sevgi Two-way Split-Step Fourier and Finite Element based Parabolic Equation Propagation Tools: Comparisons and Calibration

    IEEE AP-S International Symposium on Antennas and Propagation and USNC/URSI National Radio Science Meeting,

    July 11 - 17, Sheraton Toronto Centre Hotel, ON, Canada.

    2010
    9 O.Ozgun, R.Mittra, M.Kuzuoglu A Version of the Characteristic Basis Finite Element Method (CBFEM) by Utilizing Physical Optics for Large-scale Electromagnetic Problems

    IEEE AP-S International Symposium on Antennas and Propagation and USNC/URSI National Radio Science Meeting,

    vols. 1-6, pp. 497-500, June 1-5, Charleston, SC, USA.

    2009
    8 O.Ozgun, R.Mittra, M.Kuzuoglu Characteristic Basis Finite Element Method (CBFEM) - A Non-iterative Domain Decomposition Finite Element Algorithm for Solving Electromagnetic Scattering Problems

    IEEE AP-S International Symposium on Antennas and Propagation and USNC/URSI National Radio Science Meeting,

    vols. 1-9, pp. 4130-4133, July 5-12, San Diego, California, USA.

    2008
    7 O.Ozgun, M.Kuzuoglu A Non-iterative Domain Decomposition Method for Finite Element Analysis of 3D Electromagnetic Scattering Problems

    IEEE AP-S International Symposium on Antennas and Propagation and USNC/URSI National Radio Science Meeting,

    vols. 1-9, pp. 4142-4145, July 5-12, San Diego, California, USA.

    2008
    6 O.Ozgun, M.Kuzuoglu Electromagnetic Reshaping via Anisotropic Metamaterials

    IEEE AP-S International Symposium on Antennas and Propagation and USNC/URSI National Radio Science Meeting,

    vols. 1-9, pp. 3259-3262, July 5-12, San Diego, California, USA.

    2008
    5 O.Ozgun, R.Mittra, M.Kuzuoglu Parallelized Characteristic Basis Finite Element Method (CBFEM-MPI) - A Non-iterative Domain Decomposition Approach for Large-scale Electromagnetic Problems

    The 9th Inter. Workshop on Finite Elements for Microwave Engineering,

    May 8-9, Bonn, Germany.

    2008
    4 O.Ozgun, R.Mittra, M.Kuzuoglu Characteristic Basis Finite Element Method (CBFEM-MPI) - A Parallel, Non-iterative Domain Decomposition Algorithm for the Solution of Large-scale Electromagnetic Scattering Problems

    EWS Vth International Workshop on Electromagnetic Wave Scattering,

    October 22-25, Antalya, Turkey.

    2008
    3 O.Ozgun, M.Kuzuoglu Realization of Anisotropic Metamaterials via Coordinate Transformation

    EWS Vth International Workshop on Electromagnetic Wave Scattering,

    October 22-25, Antalya, Turkey.

    2008
    2 O.Ozgun, M.Kuzuoglu Locally-conformal and Multi-center Perfectly Matched Layer Implementations for Finite Element Mesh Truncation

    IEEE AP-S International Symposium and USNC/URSI National Radio Science Meeting,

    pp. 1753-1756, July 9-14, Albuquerque, USA.

    2006
    1 O.Ozgun, S.G.Tanyer, C.B.Erol An examination of the Fourier split-step method of representing electromagnetic propagation in the troposphere

    IEEE IGARSS International Geoscience and Remote Sensing Symposium,

    vol.6, pp. 3548-3550, June 24-28, Toronto, Canada.

    2002

     

    NATIONAL REFEREED CONFERENCE PAPERS
    No Author(s) Title Conference Year
    13 G.Y. Altun, Ö.Özgün Dünya Yüzeyi Üzerindeki Bir Hedeften Elektromanyetik Dalga Saçılımının Karma Nümerik Yöntemlerle Modellenmesi

    URSI-Türkiye 2018 9. Bilimsel Kongresi,

    6-8 Eylül, Konya, Ankara.

    2018
    12 C.Pay, Ö.Özgün Koordinat Dönüşümü Tekniğine Dayanarak Tasarlanan Yön-Bağımsız Dielektrik Katmanlar İle Radar Kesit Alanı Azaltma

    URSI-Türkiye 2018 9. Bilimsel Kongresi,

    6-8 Eylül, Konya, Ankara.

    2018
    11 M.E.Ergüden, Ö.Özgün LKB, NWA, NRL, TOGA-COARE, NPS Buharlaşma Oluk Modellerinin Karşılaştırılmalı Analizi

    URSI-Türkiye 2018 9. Bilimsel Kongresi,

    6-8 Eylül, Konya, Ankara.

    2018
    10 H. Gülbaş, Ö.Özgün, M.Kuzuoğlu Sonlu Elemanlar Yöntemiyle Yarık Halka Rezonatörlerin Saçılma Parametrelerinin Hesaplanması

    URSI-Türkiye 2016 8. Bilimsel Kongresi,

    1-3 Eylül, ODTÜ, Ankara.

    2016
    9 Ö.Özgün, G.Apaydın, M.Kuzuoğlu, L.Sevgi PETOOL: Elektromanyetik Propagasyon Analiz Sistemi

    SAVTEK 6. Savunma Teknolojileri Kongresi,

    20-22 Haziran, ODTÜ, Ankara.

    2012
    8 M.Kuzuoğlu, Ö.Özgün Dalgalı Deniz Yüzeyi Üzerinde Bulunan Cisimlerden Saçılma Probleminin Sonlu Elemanlar Yöntemiyle İstatistiksel Analizi

    SAVTEK 6. Savunma Teknolojileri Kongresi,

    20-22 Haziran, ODTÜ, Ankara.

    2012
    7 Ö.Özgün, M.Kuzuoğlu, R.Mittra Çok Ölçekli Elektromanyetik Problemlerin Etkin Çözümü İçin Geliştirilen Sonlu Elemanlar / Dipol Moment Yöntemi

    URSI-Türkiye 2010 5. Bilimsel Kongresi,

    25-27 Ağustos, ODTÜ - Kuzey Kıbrıs Kampüsü, KKTC.

    2010
    6 G.Apaydın, Ö.Özgün, M.Kuzuoğlu, L.Sevgi Yer Dalgaları Yayılımlarının Farklı Açılardan Ele Alınarak İncelenmesi

    URSI-Türkiye 2010 5. Bilimsel Kongresi,

    25-27 Ağustos, ODTÜ - Kuzey Kıbrıs Kampüsü, KKTC.

    2010
    5 G.Apaydın, Ö.Özgün, M.Kuzuoğlu, L.Sevgi Binalar Arasındaki Dalga Yayılımlarının Sonlu Elemanlar Yöntemi Kullanarak İki Yönlü Parabolik Denklem Çözümü ile Gösterilmesi

    URSI-Türkiye 2010 5. Bilimsel Kongresi,

    25-27 Ağustos, ODTÜ - Kuzey Kıbrıs Kampüsü, KKTC.

    2010
    4 Ö.Özgün, M.Kuzuoğlu, R.Mittra Karakteristik Baz Sonlu Elemanlar Yöntemi - Büyük Ölçekli Elektromanyetik Problemlerin Çözümünde Kullanılan Paralel ve Özyinelemesiz Bölge Ayrışım Algoritması

    URSI-Türkiye 2008 4. Bilimsel Kongresi,

    20-22 Ekim, Antalya.

    2008
    3 Ö.Özgün, M.Kuzuoğlu Koordinat Dönüşümü Yöntemiyle Tasarlanan Yön-bağımlı Metamateryallerin Elektromanyetikteki Yeni Uygulamaları

    URSI-Türkiye 2008 4. Bilimsel Kongresi,

    20-22 Ekim, Antalya.

    2008
    2 Ö.Özgün, M.Kuzuoğlu Sonlu Elemanlar Yöntemi Ağ Sonlandırılmasında Kullanılan Yerel-uyumlu ve Çok-merkezli Tamamen Eşlenmiş Katman Yaklaşımları

    URSI-Türkiye 2006 3. Bilimsel Kongresi,

    6-8 Eylül, Hacettepe Üniversitesi, Ankara.

    2006
    1 Ö.Özgün, S.G.Tanyer Troposferdeki elektromanyetik yayılımın hesaplanmasında Fourier adımlama yönteminin başarımının incelenmesi

    URSI-2002 1. Ulusal Kongresi,

    18-20 Eylül, İTÜ, İstanbul.

    2002

     

    THESES
    Type Title Year
    PhD Finite element modeling of electromagnetic radiation / scattering problems by domain decomposition (supervisor: Prof. Dr. Mustafa Kuzuoğlu) 2007
    MSc Dual-frequency operation of probe-fed rectangular microstrip antennas with slots: analysis and design (supervisor: Prof. Dr. İrşadi Aksun) 2001

     

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    Projects

    No Responsibility Description Year
    5 Project director

    Hacettepe University Research Fund (Project no: FBA-2016-9954)

    Development of Microwave Imaging Algorithms based on Coordinate Transformations for Detection of Cancerous Tissues

    March2016 - March 2017
    4 Consultant

    TÜBİTAK-İltaren (ÇAFRAD project - phase I)

    Radar performance analysis algorithms

    July2014 - Dec2014
    3 Project director

    TEDU Research Fund (Project no: 12B301)

    Visual Application Tools for Undergraduate Education in Electrical and Electronics Engineering

    Jan2013 - Jan2014
    2 Project director

    TÜBİTAK-ARDEB 1001 Project (Project no: 109E169)

    Efficient Numerical Modeling of Electromagnetic Problems by Designing Novel Anisotropic Metamaterial Specifications

    July2010 - Jan2012
    1 Researcher

    ASELSAN (FİSAG project - phase II)

    Developing statistical classification algorithms in MATLAB in conjunction with a warning system

    April-Sept 2010

     

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    Courses

    Hacettepe U.
    Description Year

    ELE 620 Electromagnetic Wave Propagation

    Fall 2015, 2016, Spring 2019

    ELE 624 Electromagnetic Wave Theory II

    Spring 2018

    ELE 626 Computational Methods in Electromagnetics

    Spring 2016, Fall 2017, 2018

    ELE 629 Special Topics in Electromagnetics

    (Finite Element Method for Electromagnetic Applications)

    Spring 2015, Fall 2016
    ELE 244 Electromagnetics I Spring 2015, 2016, 2017, 2018, Fall 2018
    ELE 345 Electromagnetics II Fall 2015, Summer 2016
    ELE 444 Antennas and Propagation Spring 2017, 2019
    ELE 401 Project I Fall 2015, 2016, 2017, 2018
    ELE 402 Project II Spring 2015, 2016, 2017, 2018, 2019

     

    TEDU
    Description Year
    EE 341 Electromagnetic Fields and Waves Fall 2014
    MATH 101 Calculus of One Variable Spring 2014
    MATH 203 Linear Algebra and Differential Equations Fall 2013, 2014
    MATH 204 Vector and Complex Calculus Spring 2014

     

    METU
    Description Year
    EE 224 Electromagnetic Theory Fall 2008, 2009, 2010, 2011
    EE 230 Probability and Random Variables Spring 2009, 2010, 2011, 2012
    EE 281 Electrical Circuits Fall 2008, 2009, 2010
    EE 303 Electromagnetic Waves Fall 2008, 2009, 2010, 2011
    EE 306 Signals and Systems II Spring 2009, 2010, 2011, 2012
    EE 426 Antennas and Propagation Spring 2011, 2012
    EE 493 Engineering Design I Fall 2010, 2011
    EE 494 Engineering Design II Spring 2011, 2012
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    Students

    No Student Name Type Title Year
    6 Gül Yesa Altun M.Sc., HU Numerical Modeling of Electromagnetic Backscattering by an Air Target above the Earth’s Surface (Dünya Yüzeyinden Yukarıdaki bir Hedeften Elektromanyetik Geri Saçılımın Nümerik Modellenmesi) in progress
    5 Canberk Pay M.Sc., HU Development of Radar Cross Section Reduction Techniques based on the Concept of Transformation Electromagnetics (Dönüşüm Elektromanyetiği Kavramına Dayanan Radar Kesit Alanı Azaltma Tekniklerinin Geliştirilmesi) 2018
    4 Muhsin Eren Ergüden M.Sc., HU Development of Evaporation Duct Algorithms for Two-Way Parabolic Wave Modeling of Electromagnetic Propagation (Elektromanyetik Dalga Yayılımının Çift Yönlü Parabolik Dalga Modellemesi İçin Buharlaşma Oluk Algoritmalarının Geliştirilmesi) 2018
    3 Hüseyin Gülbaş M.Sc., METU (cosupervision)

    Finite Element Modeling of Scattering from Objects in Rectangular Waveguides

    2017
    2 Özüm Emre Aşırım M.Sc., METU (cosupervision) Investigation of rough surface scattering of electromagnetic waves using finite element method 2013
    1 Ali Kemal Kazar M.Sc., METU (cosupervision) Monte Carlo analysis of the effects of material and shape uncertainties on radar cross section by the finite difference time domain method 2013
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    Research - 1

    Transformation Electromagnetics (TEM)

    1) Reshaping

    Metamaterials –artificial materials with engineered electromagnetic properties—is a young but rapidly growing topic that breaks down traditional rules, and fascinates scientists in the field of physics, optics and electromagnetics. One of the major breakthroughs in the development of metamaterials is the cloaking device for obtaining electromagnetic invisibility, which can bend light around an object as if it weren't there. The design of the cloaking device is realized by the coordinate transformation technique, which is based on the fact that Maxwell’s equations are form-invariant under coordinate transformations. In other words, Maxwell’s equations preserve their form inside the transformed space, but the medium transforms into an anisotropic medium so that the electromagnetic fields are tuned by the coordinate transformation. Although the coordinate transformation technique has long been used in electromagnetic/physics, the novel interpretation of this technique realizing a cloaking device has emerged as one of the most exciting subjects in science and the general public alike. Being inspired by the cloaking device, we have focused on the design of anisotropic metamaterials using coordinate transformation techniques to control the propagation of electromagnetic fields in several useful applications. Our initial works on this topic were among the first attempts in designing such metamaterial structures. The purposes of these works were as follows: (i) reshaping objects in electromagnetic scattering via metamaterial coatings (this technique is a generalization of the cloaking approach for invisibility, and can be used to reduce the radar cross-section (RCS) of the objects); and (ii) reshaping and miniaturizing waveguides via metamaterial fillings.

    Please refer to [7], [8], [14], [21], [35] in "international journal papers"; to [2] in "papers in other indexed international journals"; to [3], [6] in "international refereed conference papers"; to [3] in "national refereed conference papers", and to the book chapter in "Publications" section.

    Click on the figures to enlarge

     

    2) Transformation Electromagnetics-aided Computational Electromagnetics

    The reshaping approach inspired us to use the principles of transformation electromagnetics (TEM) to alleviate certain difficulties that arise in CEM methods. Therefore, we named such materials as "software metamaterials". The central idea is to modify the computational domain of the finite methods (such as the finite element method (FEM), or finite difference time domain method (FDTD)) and to place coordinate transformation-based metamaterial structures within the modified domain, and thus, to devise simple and efficient computer-aided simulation tools. Within this context, we worked on two approaches: (i) A method to fit curved geometries to a simple Cartesian grid or mesh in the finite methods. This technique can be helpful especially in the FDTD method in alleviating the effects of errors introduced by the staircasing approximation of curved geometries that do not conform to a Cartesian grid. (ii) Domain compression method to compress the excessive white space. (iii) Methods for solving electromagnetic boundary value problems involving large-scale or multi-scale features with multiple length or frequency scales or both. Multi-scale problems, in general, suffer from difficulties in mesh generation and the number of unknowns due to certain meshing requirements dictated by the fine features of the problem. Our metamaterial-based techniques allow uniform and easy-to-generate meshes by creating a virtual equivalent problem acting like the original problem.

    Please refer to [11], [20], [26], [28], [36] in "international journal papers"; to [2], [3] in "papers in other indexed international journals"; to [12], [19], [20], [21], [22], [24] in "international refereed conference papers"; and to the book chapter in "Publications" section.

    Click on the figures to enlarge

     

    3) Transformation Electromagnetics-aided Stochastic Electromagnetics (rough surface scattering problems)

    When an object is placed near or within a "random" medium, the interaction or multiple scattering of both incident and scattered waves with the medium cause variations in the radar cross-section (RCS) of the object. A proper statistical characterization of the rough scattering problem is essential to understand the multiple scattering phenomenon in random media and rough surfaces. This topic is vital in a wide range of real-life applications, such as target detection and tracking, imaging and remote sensing, radar surveillance, and so on. To analyze this composite problem statistically, Monte Carlo technique can be realized by generating a set of random rough surfaces from a given probability distribution, and by solving the problem involving each surface using a numerical method. In this manner, a family of fields is generated arising from the repeated solutions, which are considered as the samples of a random process. Afterwards, various statistical parameters (such as mean, variance, probability density function, correlation functions, etc.) can be extracted from this random process. In this technique, one challenging issue is the repeated solution of the problem, which may put a heavy burden on computational resources. For example, if N number of surfaces are generated and if the problem is to be solved by using a finite method (such as finite element method), the mesh must be generated N times with respect to each surface and the problem must be solved N times. Given the large number of realizations and large size of the problem, computation time increases dramatically. We have proposed some computational models that make efficient repeated solutions in the Monte Carlo simulation of rough surface scattering problems by utilizing the concept of transformation electromagnetics. The main advantage is the ability to employ the same mesh in all realizations of the Monte Carlo simulation. Therefore, instead of generating the mesh N times, a single mesh is created over the smooth object and only the material parameters are altered for each of N surfaces. This achieves considerable saving in time and memory, and simplifies the mesh generation process.

    Please refer to [29], [30], [31], [33], [34] in "international journal papers"; to [2] in "papers in other indexed international journals"; to [1] in "national journal papers"; to [23], [25], [27] in "international refereed conference papers"; to [8] in "national refereed conference papers" in "Publications" section.

    Click on the figures to enlarge

     

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    Research - 2

    Parabolic Equation Tool (PETOOL)

    Program download

     

    Fig. 2 in "Applying the Parabolic Equation to Tropospheric Groundwave Propagation", which is a review of recent achievements and significant milestones in the field of parabolic equation (PE) modeling, written by P. Zhang, L. Bai, Z. Wu, and L. Gu, in "IEEE Antennas and Propagation Magazine" in June 2016 (vol. 58, pp. 31-44) Link .
  • Image
  • (Click to enlarge)

    Radio-wave propagation over the Earth’s surface and in an inhomogeneous atmosphere is affected by several scattering phenomena, such as reflection, refraction, and diffraction. The rigorous analytical and numerical modeling of radio-wave propagation in such environments is a challenging task and has attracted the attention of researchers for many decades. The difficulty stems from the vast variability of the properties of the medium and also the surfaces and obstacles that re-direct the propagating energy, making the radio wave propagation somewhat unpredictable. Parabolic Equation (PE) model has been widely used in propagation modeling to predict the wave behavior between a transmitter and a receiver over the two-dimensional Earth’s surface, because of its high capability in modeling both horizontally- and vertically-varying atmospheric refraction (especially ducting) effects. However, standard PE handles only the forward-propagating waves (hence called one-way PE), and neglects the backscattered waves. The forward waves provide almost accurate results for typical long-range propagation problems, only if there does not exist obstacles that redirect the incoming wave in the form of reflections and diffractions. However, the accurate estimation of the multipath effects, occurring during propagation over terrain, requires the correct treatment of backward waves as well.

    In 2009, I developed a two-way PE algorithm incorporating the backward-propagating waves into the standard one-way PE by utilizing an iterative forward-backward scheme for modeling multipath effects over a staircase-approximated terrain. This paper, which was published in Sept. 2009, has immediately initiated a collaboration with Dr. Sevgi, Dr. Apaydin and Dr. Kuzuoglu. We have developed a MATLAB-based software tool (called PETOOL) with a graphical user interface for educational/research purposes, and our computer codes are available for public use.

    Please refer to [12], [22], [23], [25], [32] in "international journal papers"; to [10], [11], [17] in "international refereed conference papers"; to [5], [6], [9] in "national refereed conference papers" in "Publications" section.

    Click on the figures to enlarge

     

    Click the video below to see the short demo of PETOOL:

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    Research - 3

    Electromagnetic Tools

    1) GO+UTD (Geometrical Optics and Uniform Theory of Diffraction Toolbox)

    A MATLAB-based tool (GO+UTD) with a user-friendly graphical user interface (GUI) for the simulation of electromagnetic wave propagation and diffraction effects over variable terrain by using the geometrical optics (GO) and the uniform theory of diffraction (UTD) techniques.

    Program download

    Please refer to [41] for details.

     

    2) VectGUI Tool

    A simple MATLAB tool that visualizes functions and operators (e.g., gradient of scalar fields and divergence of vector fields) in the cylindrical and spherical coordinate systems.

    Program download

    Please refer to [37] for details.

     

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    Research - 4

    Domain Decomposition Finite Element Algorithms

    Finite Element Method (FEM) is a variational method developed for the approximate solution of Boundary Value Problems (BVPs) governed by partial differential equations, and is one of the most important developments in the history of computational methods, due to its two main advantages: (i) Flexibility to handle any type of geometry and material inhomogeneity without a need to alter the formulation or the computer code (geometrical fidelity). (ii) Low memory and CPU time requirements due to its highly sparse and banded matrix structure. The most distinctive feature of the FEM is the division of a given domain into a set of simple subdomains, called finite elements. The original domain (i.e., the FEM mesh) is then considered as an assembly of these elements connected at a finite number of preselected points, called nodes. The basic principle of the method is to replace the entire continuous domain with some number of finite elements in which the function is represented as a linear combination of some simple basis functions (also called shape, approximation or interpolation functions) with unknown coefficients. Hence, the solution of the entire system is approximated by a number of finite unknown coefficients. Then, the local system of algebraic relations is derived in each element by applying the Rayleigh-Ritz Method or most commonly the Weighted Residual Method (with Galerkin procedure). Finally, the local system of equations is assembled to obtain the global system of equations to solve for the unknown function.

    In high-frequency applications (such as the calculation of the RCS of large targets, analysis and design of radar and communication systems), the FEM requires an electrically-large computational domain, implying a large number of unknowns, such that the numerical solution of the problem is not feasible even on state-of-the-art computers. Although the resultant matrix is sparse and can be stored by using a compressed storage scheme, the use of iterative solvers for these matrices usually creates a heavy burden on CPU memory and time due to the slow and unstable behavior of the convergence, even when accelerated by means of preconditioners. Hence, alternative techniques, such as the domain decomposition (DD) methods, have been employed to alleviate this difficulty. A general DD approach, which is based on the divide-and-conquer philosophy, breaks down a large-scale problem into a number of small subproblems whose solution is manageable. The subdomains are solved iteratively (or non-iteratively in some cases) by appropriately communicating with the others. Then, the solution of the original (whole) problem is reached by assembling the solution of all subdomains. A DD method is intrinsically suitable for the parallel computation of the subdomains, providing a further decrease in the overall computation time.

    In the context of FEM, we have developed alternative domain decompositon techniques as below:

     

    1) Characteristic Basis Finite Element Method (CBFEM)

    My postdoctoral research in Pennsylvania State University concentrated on a novel domain decomposition finite element algorithm (called Characteristic Basis Finite Element Method (CBFEM)) that is tailored to a wide class of electromagnetic boundary problems, covering both quasi-static and time-harmonic regimes, by using the concept of Characteristic Basis Functions (CBFs). This is a non-iterative matrix-reduction technique, and is well-suited to the implementation of parallel processing techniques using such as the Message Passing Interface (MPI) library. Basically, this method utilizes a set of specially-defined CBFs in conjunction with a domain decomposition scheme that partitions the computational domain into a number of non-overlapping subdomains. The CBFs—macro-domain basis functions that are constructed in each subdomain by considering the physics of the problem—were originally proposed by Dr. Raj Mittra to solve time-harmonic electromagnetic problems in the context of the Method of Moments. he basic steps of the CBFEM technique are as follows: (i) partition the computational domain into a number of subdomains, and generate the CBFs tailored to each individual subdomain; (ii) express the unknowns as a series of these CBFs that are weighted with unknown coefficients yet to be determined; (iii) transform the original matrix into a "smaller" one (i.e., reduced matrix) by using the Galerkin procedure, which uses the CBFs as both basis and testing functions; (iv) solve the reduced matrix for the unknown coefficients, and substitute the coefficients into the series expressions to obtain the unknown quantities inside the entire computational domain. Common attributes of the CBFEM are: (i) capability to reduce the matrix size; (ii) non-iterative nature; and (iii) convenient parallelization, which decreases the memory and overall computation time when run on multiple processors.

    First, we concentrated on the implementation of CBFEM in the static regime by generating the CBFs via point charges, and developed 3D parallel FEM and mesh generation codes to compute the capacitance matrices of 3D interconnect structures, which include vias, crossovers and bends, in integrated circuit packaging. Second, we extended this method to the dynamic case, and dealt with the RCS computation of large objects in 3D electromagnetic scattering problems by employing different approaches (such as hybridizing CBFEM with physical optics (PO) approach, generating the CBFs via dipole-type sources, or multi-level approach that applies CBFEM in a nested manner, etc.).

    Please refer to [13], [15], [16], [18], [19], [24], [27] in "international journal papers"; to [4], [5], [8], [9], [13], [15], [16] in "international refereed conference papers"; to [4] in "national refereed conference papers" in "Publications" section.

    Click on the figures to enlarge

     

    2) Iterative Leap-field Domain Decomposition Method (ILF-DDM)

    The main idea of the ILF-DDM approach is the iterative application of the Huygens' (or equivalence) Principle to the fields radiated by the equivalent currents calculated in each iteration. In other words, in each iteration, each subproblem is solved and equivalent currents are calculated using the fields radiated from the sources contained in other subdomains, and these currents are reradiated over all other subdomains, until a condition for convergence is satisfied. The most distinguished feature of the ILF-DDM approach is the utilization of the locally-conformal PML concept along the boundaries of the subdomains. With the aid of the locally-conformal PML approach, the ILF-DDM algorithm can be applied to not only cases involving multiple objects but also problems containing a single challenging object in FEM applications. In addition to this, due to the special character of the locally-conformal PML approach and the FEM, the ILF-DDM creates 'smaller' subdomains because the locally-conformal PML can be designed as conformal and very close to the surface of the object. The solution of each small subproblem is reduced to the solution of an ordinary scattering problem with appropriately defined boundary conditions, but with fewer unknowns. Thus, the most appealing advantage of the method is considerable reduction in memory requirements and computation time. It is observed that convergence is achieved after a few iterations and computation time may further be reduced via the parallel solution of the subproblems.

    Please refer to [10], [17] in "international journal papers" in "Publications" section.

    Click on the figures to enlarge

     

    3) Forward-Backward Domain Decomposition Method (FB-DDM)

    The FB-DDM is established on the classical alternating Schwarz method with overlapping subdomains. However, the FB-DDM implements the Schwarz method by taking into account certain physical aspects of the original (whole) problem. That is, the Schwarz method is improved in terms of efficiency and rate of convergence by considering the geometry of the problem and the expected field behavior inside the original domain. This is achieved by the implementation of the locally-conformal PML (perfectly matched layer) method along the boundaries of the subdomains. In some problems involving smooth geometries, the FB-DDM converges in just a single forward iteration (i.e., the method is non-iterative), where the problem in each subdomain is solved only once by appropriately defined subdomains and additional PML regions attached to each subdomain. In other challenging geometries, the initial forward iteration of the FB-DDM provides an initial guess 'close' to the exact values of the boundary conditions (BCs) of each subdomain, unlike the 'arbitrary' initial guess in the Schwarz method. After the initial forward iteration, the problems defined on the subdomains are solved iteratively, similar to the Schwarz method, in a forward-backward fashion until convergence is achieved. It is obvious that the better initial guess for the BCs provides an increased convergence rate by decreasing the number of the forward-backward iterations during the field refinement process. In addition, the proposed method provides a considerable reduction in the memory requirements and computation time.

    Please refer to [6] in "international journal papers";and to [7] in "international refereed conference papers" in "Publications" section.

    Click on the figures to enlarge

     

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    Research - 5

    Perfectly Matched Layer (PML) Algorithms

    In the numerical solution of open-region electromagnetic radiation and/or scattering problems via finite methods (such as the finite element method FEM, and the finite difference time domain method FDTD), the unbounded physical domain must be truncated by an artificial boundary or layer to achieve a bounded computational domain. One of the most widely-used approaches is to employ a Perfectly Matched Layer (PML), which is an artificial anisotropic layer absorbing outgoing plane waves irrespective of their frequency and angle of incidence, without any reflection. In other words, the PML medium achieves smooth field decay to couple the computational domain to the free-space region of infinite extent without any undesirable reflections. The main advantage of the PML is the minimization of the white space (i.e., free-space) due to its close proximity and conformity to the surface of the object. Almost all of the PML realizations introduced so far in the literature have been implemented in a rectangular prism that does not have arbitrary curvature discontinuities.

    The novel PML methods (called "Locally-conformal PML" and "Multi-center PML" methods) that we have developed recently utilize specially- and locally-defined complex coordinate transformations, and thus, make possible the easy design of conformal PMLs having challenging geometries, especially having some intersection regions or abrupt changes in curvature. Such conformal PML domains are very crucial especially in radiation and scattering problems, because they decrease the computational demand (such as memory and processing power) on account of a minimization of the white space. The locally-conformal PML and multi-center PML methods are designed in complex space by just replacing the real coordinates with their complex counterparts calculated in terms of the complex coordinate transformation. In their formulations, Maxwell's equations are modified accordingly inside the complex space, and the elements in the real coordinate system are mapped to the complex elements (i.e., elements whose nodal coordinates are complex) in complex space. Then, the weak variational form of the wave equation is discretized using these complex elements which are determined by the complex coordinate transformation.

    Please refer to [2], [3], [4], [5], [9] in "international journal papers"; to [2] in "international refereed conference papers"; to [2] in "national refereed conference papers" in "Publications" section.

    Click on the figures to enlarge

     

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    Contact Information

    Address

    Hacettepe University
    Department of Electrical and Electronics Engineering
    06800 Beytepe, Ankara, TURKEY

    Phone (1): (+90) 312-297-70-70
    Phone (2): (+90) 312-780-70-70
    Email: ozlem [at] ee.hacettepe.edu.tr

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