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The Resource Characteristic Mode Analysis of Crumpled Graphene Flakes and A New Green's Functions Evaluation Method for Layered Media, by Kalyan C. Durbhakula

Characteristic Mode Analysis of Crumpled Graphene Flakes and A New Green's Functions Evaluation Method for Layered Media, by Kalyan C. Durbhakula

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Author
Contributor
Summary
Graphene {uFB02}akes (GFs) in real composites are rarely perfectly {uFB02}at, and often exhibit complicated crumpled shapes. Therefore, the goal of this work was to quantify the electromagnetic scattering characteristics of individual crumpled GFs with shapes resembling those found in real composites. The extinction cross sections of tens of GFs, with different sizes and various levels of crumpleness, were calculated using multiple independent solvers. The results show that resonances in the extinction cross section spectrum decrease in amplitude as the GFs become more crumpled. Moreover, some crumpled GFs exhibited a broader resonance than that of perfectly {uFB02}at GFs. To explain these results, we used a characteristic mode analysis to decompose the graphene surface currents into a set of fundamental currents or modes. For perfectly {uFB02}at square GFs, the vertical and horizontal modes were found to overlap and resonate at the same frequencies. However, as the GFs became more crumpled, the horizontal/vertical symmetry broke down causing the corresponding modes to separate and resonate at different frequencies leading to an overall broader bandwidth. These results attest to the importance of modeling the exact shape of GFs to accurately characterize their electromagnetic response. In the second year of my Ph.D. program, a slightly different path has been employed to develop a new method of Green's functions evaluation that will eventually help with the electromagnetic scattering and propagation analysis of printed circuit board traces. With this goal in mind, modi{uFB01}ed Green's function equations have been developed that were validated with existing numerical methods and commercially available electromagnetic wave solvers. The modi{uFB01}ed Green's function method, otherwise called as analytical evaluation method, which replaces the tail region of Sommerfeld integrals with its equivalent closed form expressions. Further, a detailed study on the types of contours has been carried out to understand their merits and demerits. Finally, the best available contour method has been identi{uFB01}ed in conjunction with the analytical evaluation method. This combined technique has been applied to the Green's functions of a single dielectric layer backed by a perfect electric conductor. This combination displayed good convergence even for the most dif{uFB01}cult case of zero vertical separation between the source and observation points in the space-domain system. Later, the modi{uFB01}ed Green's functions were applied to the method of moments solution to obtain surface currents of PCB traces. In addition to full or semi-numerical studies of Green's functions, the identi{uFB01}cation of complex pole locations was also carried out. In this work, the Mittag-Lef{uFB02}er (ML) expansion method has been applied to identify the initial locations of surface wave (SW) and leaky wave (LW) poles lying in the proper and improper sheet of Riemann surface (RS), respectively. To validate the accuracy and robustness of the proposed method, a detailed comparative analysis has been carried out between the ML expansion method and existing methods. The ML expansion method converts the transverse magnetic (TM) and transverse electric (TE) characteristic mode equations from transcendental to polynomial equations. The initial pole locations can be re{uFB01}ned using either conventional root-{uFB01}nding methods or Padè approximants. Numerical results for electrically thick, lossless and lossy substrates shows that the ML expansion has superior convergence properties. Further, a detailed study on numerical convergence of SW and LW poles to their {uFB01}nal roots is discussed. The ML expansion method is one of the less known methods that can ef{uFB01}ciently identify and differentiate between the aforementioned type of poles. The transition region between LW and SW poles for electrically thick substrates (ETS) is minimally studied and efforts have been made in this work to understand and identify them as the frequency or dielectric constant changes. In addition, a convergence study of ML expansions has been carried out when applied to TE and TM modes of a single dielectric layered medium backed by a ground plane. Finally, the RF coupling experiments to PCB were debugged, analyzed and explained using CMA. The analysis has shown a match in coupling frequency between measurement and simulation and has shown hotspots on PCB indicating maximum and minimum regions for RF coupling. Further, the research was extended to PCB traces with matched loads and the CMA has shown signi{uFB01}cant promise in understanding RF coupling
Language
eng
Work
Publication
Extent
1 online resource (187 pages)
Note
  • "A dissertation in Electrical and Computer Engineering and Physics."
  • Advisor: Deb Chatterjee
  • Vita
Instance
Label
Characteristic Mode Analysis of Crumpled Graphene Flakes and A New Green's Functions Evaluation Method for Layered Media
Title
Characteristic Mode Analysis of Crumpled Graphene Flakes and A New Green's Functions Evaluation Method for Layered Media
Statement of responsibility
by Kalyan C. Durbhakula
Creator
Contributor
Author
Degree supervisor
Subject
Genre
Language
eng
Summary
Graphene {uFB02}akes (GFs) in real composites are rarely perfectly {uFB02}at, and often exhibit complicated crumpled shapes. Therefore, the goal of this work was to quantify the electromagnetic scattering characteristics of individual crumpled GFs with shapes resembling those found in real composites. The extinction cross sections of tens of GFs, with different sizes and various levels of crumpleness, were calculated using multiple independent solvers. The results show that resonances in the extinction cross section spectrum decrease in amplitude as the GFs become more crumpled. Moreover, some crumpled GFs exhibited a broader resonance than that of perfectly {uFB02}at GFs. To explain these results, we used a characteristic mode analysis to decompose the graphene surface currents into a set of fundamental currents or modes. For perfectly {uFB02}at square GFs, the vertical and horizontal modes were found to overlap and resonate at the same frequencies. However, as the GFs became more crumpled, the horizontal/vertical symmetry broke down causing the corresponding modes to separate and resonate at different frequencies leading to an overall broader bandwidth. These results attest to the importance of modeling the exact shape of GFs to accurately characterize their electromagnetic response. In the second year of my Ph.D. program, a slightly different path has been employed to develop a new method of Green's functions evaluation that will eventually help with the electromagnetic scattering and propagation analysis of printed circuit board traces. With this goal in mind, modi{uFB01}ed Green's function equations have been developed that were validated with existing numerical methods and commercially available electromagnetic wave solvers. The modi{uFB01}ed Green's function method, otherwise called as analytical evaluation method, which replaces the tail region of Sommerfeld integrals with its equivalent closed form expressions. Further, a detailed study on the types of contours has been carried out to understand their merits and demerits. Finally, the best available contour method has been identi{uFB01}ed in conjunction with the analytical evaluation method. This combined technique has been applied to the Green's functions of a single dielectric layer backed by a perfect electric conductor. This combination displayed good convergence even for the most dif{uFB01}cult case of zero vertical separation between the source and observation points in the space-domain system. Later, the modi{uFB01}ed Green's functions were applied to the method of moments solution to obtain surface currents of PCB traces. In addition to full or semi-numerical studies of Green's functions, the identi{uFB01}cation of complex pole locations was also carried out. In this work, the Mittag-Lef{uFB02}er (ML) expansion method has been applied to identify the initial locations of surface wave (SW) and leaky wave (LW) poles lying in the proper and improper sheet of Riemann surface (RS), respectively. To validate the accuracy and robustness of the proposed method, a detailed comparative analysis has been carried out between the ML expansion method and existing methods. The ML expansion method converts the transverse magnetic (TM) and transverse electric (TE) characteristic mode equations from transcendental to polynomial equations. The initial pole locations can be re{uFB01}ned using either conventional root-{uFB01}nding methods or Padè approximants. Numerical results for electrically thick, lossless and lossy substrates shows that the ML expansion has superior convergence properties. Further, a detailed study on numerical convergence of SW and LW poles to their {uFB01}nal roots is discussed. The ML expansion method is one of the less known methods that can ef{uFB01}ciently identify and differentiate between the aforementioned type of poles. The transition region between LW and SW poles for electrically thick substrates (ETS) is minimally studied and efforts have been made in this work to understand and identify them as the frequency or dielectric constant changes. In addition, a convergence study of ML expansions has been carried out when applied to TE and TM modes of a single dielectric layered medium backed by a ground plane. Finally, the RF coupling experiments to PCB were debugged, analyzed and explained using CMA. The analysis has shown a match in coupling frequency between measurement and simulation and has shown hotspots on PCB indicating maximum and minimum regions for RF coupling. Further, the research was extended to PCB traces with matched loads and the CMA has shown signi{uFB01}cant promise in understanding RF coupling
Cataloging source
UMK
http://library.link/vocab/creatorName
Durbhakula, Kalyan C
Degree
Ph.D.
Dissertation note
(School of Computing and Engineering and Department of Physics and Astronomy).
Dissertation year
2019.
Granting institution
University of Missouri-Kansas City,
Illustrations
illustrations
Index
no index present
Literary form
non fiction
Nature of contents
  • dictionaries
  • bibliography
  • theses
http://library.link/vocab/relatedWorkOrContributorDate
1959-
http://library.link/vocab/relatedWorkOrContributorName
Chatterjee, Deb
http://library.link/vocab/subjectName
  • Graphene
  • Green's functions
Label
Characteristic Mode Analysis of Crumpled Graphene Flakes and A New Green's Functions Evaluation Method for Layered Media, by Kalyan C. Durbhakula
Instantiates
Publication
Copyright
Note
  • "A dissertation in Electrical and Computer Engineering and Physics."
  • Advisor: Deb Chatterjee
  • Vita
Antecedent source
not applicable
Bibliography note
Includes bibliographical references (pages 167-186)
Carrier category
online resource
Carrier category code
  • cr
Carrier MARC source
rdacarrier
Color
black and white
Content category
text
Content type code
  • txt
Content type MARC source
rdacontent
Control code
1120783202
Dimensions
unknown
Extent
1 online resource (187 pages)
File format
one file format
Form of item
online
Level of compression
mixed
Media category
computer
Media MARC source
rdamedia
Media type code
  • c
Other physical details
illustrations.
Quality assurance targets
not applicable
Specific material designation
remote
System control number
(OCoLC)1120783202
System details
  • The full text of the dissertation is available as an Adobe Acrobat .pdf file; Adobe Acrobat Reader required to view the file
  • Mode of access: World Wide Web
Label
Characteristic Mode Analysis of Crumpled Graphene Flakes and A New Green's Functions Evaluation Method for Layered Media, by Kalyan C. Durbhakula
Publication
Copyright
Note
  • "A dissertation in Electrical and Computer Engineering and Physics."
  • Advisor: Deb Chatterjee
  • Vita
Antecedent source
not applicable
Bibliography note
Includes bibliographical references (pages 167-186)
Carrier category
online resource
Carrier category code
  • cr
Carrier MARC source
rdacarrier
Color
black and white
Content category
text
Content type code
  • txt
Content type MARC source
rdacontent
Control code
1120783202
Dimensions
unknown
Extent
1 online resource (187 pages)
File format
one file format
Form of item
online
Level of compression
mixed
Media category
computer
Media MARC source
rdamedia
Media type code
  • c
Other physical details
illustrations.
Quality assurance targets
not applicable
Specific material designation
remote
System control number
(OCoLC)1120783202
System details
  • The full text of the dissertation is available as an Adobe Acrobat .pdf file; Adobe Acrobat Reader required to view the file
  • Mode of access: World Wide Web

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