URSI-EMTS 2013

The “URSI Commission B School for Young Scientists” is organized by URSI Commission B and will be arranged for the first time on the occasion of EMTS 2013 in Hiroshima, Japan. This School is a one-day event held during EMTS 2013, and is sponsored jointly by URSI Commission B and the EMTS 2013 Local Organizing Committee. The School offers a short, intensive course, where a series of lectures will be delivered by two leading scientists in the Commission B community. Young scientists are encouraged to learn the fundamentals and future directions in the area of electromagnetic theory from these lectures. Some details on the School are given below.

1. Course Title

Fundamentals of Numerical and Asymptotic Methods

2. Course Program

-   Lecture 1
    Date and Time: 9:00-13:00, May 20, 2013
    Venue: International Conference Center Hiroshima (ICCH)
    Lecture Title: The Method of Moments (MoM) Applied to Problems in Electromagnetic Scattering, Radiation, and Guided Waves
    Instructor: Professor Donald R. Wilton (Dept. of ECE, University of Houston, USA)

-   Lunch: 13:00-14:00

-   Lecture 2
    Date and Time: 14:00-18:00, May 20, 2013
    Venue: International Conference Center Hiroshima (ICCH)
    Lecture Title: A Summary of Asymptotic High Frequency (HF) Methods for Solving Electromagnetic (EM) Wave Problems
    Instructor: Professor Prabhakar H. Pathak (Dept. of ECE, The Ohio State University ElectroScience Lab., USA)

3. Lecture Abstracts

Lecture 1

Date and Time: 9:00-13:00, May 20, 2013

Venue: International Conference Center Hiroshima (ICCH)

Lecture Title: The Method of Moments (MoM) Applied to Problems in Electromagnetic Scattering, Radiation, and Guided Waves

Instructor: Professor Donald R. Wilton (Dept. of ECE, University of Houston, USA)

Abstract     The Method of Moments (MoM) is the name given by Harrington to a general procedure for converting linear operator equations (e.g., linear partial differential or integral equations) into approximating systems of linear equations. MoM and the Finite Element Method (FEM) are essentially equivalent, though they have come to have slightly different connotations due to their different origins. Thus, the former is usually associated with integral equations, and the latter with partial differential equations. However, we minimize any distinctions between them, employing similar approaches to discretize both integral and partial differential equations, and to hybrid formulations in which the two are coupled.     Radiation and scattering problems are generally open region problems involving piecewise homogeneous regions. Such problems are often efficiently formulated by introducing surface currents on region boundaries via the equivalence principle. These equivalent currents are then solved for using integral equation approaches, where the Green’s functions used ensure that the radiated or scattered fields are outgoing at infinity. Integral equations arise from the imposition of boundary conditions on fields represented in terms of induced or equivalent currents on the boundaries. The equations are converted to matrix form by discretizing both the surface geometry and the equivalent currents. On conducting surfaces, the most common formulations are the electric and the magnetic field integral equations (EFIE and MFIE, respectively). Since one or both of the associated integral operators appear in almost every integral equation, their careful study is warranted. The EFIE is the more restrictive, requiring so-called divergence-conforming current representations (bases) with continuous normal components across element boundaries. However, both operators appear, for example, in the PMCHWT and Müller formulations for scattering by dielectric objects.     For interior problems or those involving extremely inhomogeneous regions, it is often more efficient to seek direct numerical solution of the vector Helmholtz wave equation. In three-dimensions, the solution domain is generally subdivided into a mesh of cubic or tetrahedral cells, with tangential vector components defined at the cell edges. The fields are then expanded in terms of interpolatory bases whose coefficients represent these tangential components; the same bases are also typically used to test the Helmholtz equation, enforcing its equality in some average sense. For the Helmholtz equation, the bases should be curl-conforming, i.e. producing field representations with continuous tangential components, even across material boundaries.     Both integral and Helmholtz equations suffer from low-frequency breakdown problems. In addition, integral equations must deal with the evaluation of singular integrals, interior resonances, and the solution of dense systems of equations. On the other hand, the solution of Helmholtz equations involves issues with preconditioning, and, for open region problems, mesh truncation. Recent advances in dealing with these issues will be discussed briefly.

Lecture 2

Date and Time: 14:00-18:00, May 20, 2013

Venue: International Conference Center Hiroshima (ICCH)

Lecture Title: A Summary of Asymptotic High Frequency (HF) Methods for Solving Electromagnetic (EM) Wave Problems

Instructor: Professor Prabhakar H. Pathak (Dept. of ECE, The Ohio State University ElectroScience Lab., USA)

Abstract     The geometrical optics (GO) ray field consists of direct, reflected and refracted rays. GO ray paths obey Fermat’s principle, and describe reflection and refraction of HF EM waves, but not the diffraction of waves around edges and smooth objects, etc. Consequently, GO predicts a zero EM field within shadow regions of impenetrable obstacles illuminated by an incident GO ray field. Early attempts by Young to predict edge diffraction via rays, and by Huygen, Fresnel and Kirchhoff to predict diffraction using wave theory will be briefly reviewed. Unlike GO, the wave based physical optics (PO) approach developed later requires an integration of the induced currents on the surface of an impenetrable obstacle illuminated by an external EM source in order to find the scattered field. The induced currents in PO are approximated by those which would exist on a locally flat tangent surface, and are set to zero in the GO shadow region. If the incident field behaves locally as a plane wave at every point on the obstacle, then it can be represented as a GO ray field; the resulting PO calculation constitutes a HF wave optical approach. PO contains diffraction effects due to the truncation of the currents at the GO shadow boundary; these effects may be spurious if there is no physical edge at the GO shadow boundary on the obstacle, whereas it is incomplete even if an edge is present at the GO shadow boundary. In the 1950s, Ufimtsev introduced an asymptotic correction to PO; his formulation is called the physical theory of diffraction (PTD). PTD = PO + ∆, where ∆ is available primarily for edged bodies. In its original form, PTD is not accurate near and in shadow zones of smooth objects without edges, nor in shadow zones for bodies containing edges that are not completely illuminated or visible. At about the same time as PTD, a ray theory of diffraction was introduced by Keller; it is referred to as the geometrical theory of diffraction (GTD). GTD was systematically formulated by generalizing Fermat’s principle to include a new class of diffracted rays. Such diffracted rays arise at geometrical and/or electrical discontinuities on the obstacle, and they exist in addition to GO rays. GTD = GO + Diffraction. Away from points of diffraction, the diffracted rays propagate like GO rays. Just as the initial values of reflected and refracted rays are characterized by reflection and transmission coefficients, the diffracted rays are characterized by diffraction coefficients. These GTD coefficients may be found from the asymptotic HF solutions to appropriate simpler canonical problems via the local properties of ray fields. Most importantly, the GTD overcomes the failure of GO in the shadow region, it does not require integration over currents, and it provides a vivid physical picture for the mechanisms of radiation and scattering. In its original form, GTD exhibits singularities at GO ray shadow boundaries and ray caustics. Uniform asymptotic methods were developed to patch up GTD in such regions. These uniform theories are referred to as UTD, UAT, spectral synthesis methods, and the equivalent current method (ECM). The pros and cons of wave optical methods (PO, PTD, ECM) and ray optical methods (GO, GTD, UTD, UAT) will be discussed along with some recent advances in PO and UTD. A UTD for edges excited by complex source beams (CSBs) and Gaussian beams (GBs) will also be briefly described; the latter may be viewed as constituting beam optical methods. A hybridization of HF and numerical methods will be briefly discussed as well.

4. Registration Fees for the School

The registration fees for the School are as follows:
-   EMTS 2013 participants (except YSA recipients): 10,000 JPY
-   Non EMTS 2013 participants: 14,000 JPY
-   YSA recipients: free

It is strongly recommended that the recipients of the EMTS 2013 Young Scientist Award (YSA) participate in the School. For those interested in the School, please visit the Registration webpage for further details at:
http://ursi-emts2013.org/registration.html

For any inquiries on the School, please contact:
    EMTS 2013 Japan Secretariat
    c/o DUPLER CORP. 3F Sun-Arch Bldg.
    3-1 Nemoto, Matsudo
    Chiba 271-0077, Japan
    Tel: +81-47-361-6030
    Fax: +81-47-308-5272
    E-mail: secretariatursi-emts2013.org