# 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

# Publications

BOOK |
---|

Author(s) | Title | Publisher | Year | |
---|---|---|---|---|

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 |
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 |
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 |
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 |
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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 | 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 | 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 | 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 | 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 | 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 | vols. 1-9, pp. 4142-4145, July 5-12, San Diego, California, USA. |
2008 |

6 | O.Ozgun, M.Kuzuoglu | Electromagnetic Reshaping via Anisotropic Metamaterials | 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 |
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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 |
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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. |
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Description | Year |
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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 |
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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 |
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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 |

# 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 |

# 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 downloadFig. 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 .

(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:

home Previous Next# 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.

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.

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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