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1 
Frequency response of E polarized sources over a lossy earth in the presence of twodimensional shielding structures.Baertlein, Brian Allen. January 1988 (has links)
Electromagnetic shielding by thin, perfectly conducting, two dimensional cylindrical shells over a lossy earth is investigated. The temporal frequency response of the exterior field due to a line source within the shell is computed for a shell described by a three sided, rectilinear structure whose opening faces the earth. The formulation allows shells of arbitrary crosssectional shape to be analyzed. The earth is modeled as a homogeneous halfspace with a planar boundary and frequency dependent electromagnetic properties. Two solution techniques are presented. In the first, the induced current is obtained through a numerical solution of the electric field integral equation (EFIE) at many discrete frequencies. It is found that the applicability of this formulation is limited since in the case of effective shielding, fields calculated from the EFIE are very sensitive to numerical errors. In the second technique the EFIE is again solved for the currents induced on the shell. The induced currents are used to calculate the electric field in the aperture which is used to solve a combinedsource integral equation (CSIE) for the external fields. It is found that the CSIE does not suffer from the numerical illconditioning that plagues the EFIE, and is well behaved at all frequencies. Numerical results are presented which indicate that the shellearth combination is very effective in shielding the internal source. Interior modes are weakly transmitted to the interior for the case of a purely dielectric earth. For a lossy halfspace the resonances of the closed shell are enhanced. The related topic of scattering by perfectly conducting objects over a lossy earth is addressed. Numerical formulations for the solution of the integral equations are presented which deal with several troublesome aspects of the problem, including the incorporation of the correct edge singularities.

2 
Electromagnetic response of thin wires over an homogeneous earth.Young, Jeffrey Lee. January 1989 (has links)
The electromagnetic response of infinitely long, thin wires over a flat earth is presented for two different applications: the shielding properties of an ensemble of parallel wires excited by a plane wave and the electromagnetic coupling of two perpendicular wires excited by a dipole. The shielding study begins with the formulation of the boundary value problem for N wires over a lossy half space. A suitable axial impedance operator is applied to obtain a system of equations whose unknowns are the currents flowing on each wire. Once the currents are determined, the aggregate field produced by the ensemble can be computed by summing N Fourier type integrals. For the specialized case of the infinite planar grid, Floquet's Theorem and Poisson's Summation Formula are invoked, transforming the linear system of equations into a closed form expression for the current flowing on each wire. We show that the electromagnetic response of the planar grid of finite extent and the grid of infinite extent are similar. For nonplanar configurations, such as the semicircular shell, shielding values of 60 dB are possible when the structure is of nonresonant dimensions; otherwise, the performance can degrade to 20 dB. In the case of the crossed wire configuration, the starting point is the development of the integral equations that govern the coupling between wires and the source; the unknowns are the spectral currents flowing in each wire. The equations are given in terms of generalized impedance functions for the situation where the wires are over a stratified earth. However, for the numerical work, only the case where the wires are in an unbounded, homogeneous medium is considered. Two numerical methods, with overlapping regions of validity, are applied: the method of moments and the method of multiple scatterers. By using the method of moments, we can obtain a matrix equation that will determine the spectral currents for any wire spacing. The multiple scatterer method leads to a more convenient matrix series solution and shows that the coupling strength is proportional to 1/d², where d is the wire separation, plus higher order inverse terms.

3 
Analysis of a test technique for hardness surveillanceMarcum, Frank. January 1988 (has links)
Thesis (M.S.)Ohio University, June, 1988. / Title from PDF t.p.

4 
Electromagnetic coupling by a wire penetrating a circular aperture in an infinite planar conducting screenLee, Robert, 1962 January 1988 (has links)
We consider the problem of electromagnetic propagation along a wire which passes through an aperture. We begin by formulating an integral equation in terms of the electric field at the aperture. The solution of the integral equation allows us to determine parameters of interest such as the equivalent admittance, the current on the wire, and the electric field. We solve the integral equation using both a zeroth order and method of moments approximation for the aperture field. From this we are able to compute the admittance and current in the frequency domain. We next calculate the current response to a transient pulse excitation. The results show that the screen provides little shielding from pulse penetration along the wire. Finally, we calculate solutions for the electric field. The results are given in several contour plots.

5 
Electromagnetic coupling by a wire through a cavitybacked circular aperture in an infinite screenWright, Diana Beth, 1963 January 1988 (has links)
The problem of a wire penetrating a circular aperture in an infinite screen and coupling energy into a cavity behind that screen is considered. We formulate an integral equation in terms of the electric field in the aperture. This integral equation is solved using two approximate methods: a zerothorder approximation valid at low frequencies, and the method of moments. In addition, we introduce an equivalent circuit model to aid in our physical interpretation of the problem. Numerical results for the interior current on the wire and for the equivalent circuit admittance parameters are presented in order to provide a comparison between the two approximations. Inside the cavity, we examine the components of the electric field as a function of position. Finally, the exterior magnetic field far from the aperture is studied as a function of frequency. We examine the relationship between interior resonance features associated with the presence of the cavity and observations of the exterior field.

6 
Investigation and development of structural composite materials for use as electromagnetic shielding agents in the current aerospace industry.20 October 2010 (has links)
Due to the nature of today's competitive electronics market, the development of new electronic / Thesis (M.Sc.Eng.)University of KwaZuluNatal, 2007.

7 
Shielding effectiveness of superalloy, aluminum, and mumetal shielding tapes a project report /Cheung, Cindy S. Mehiel, Eric A. January 1900 (has links)
Thesis (M.S.)California Polytechnic State University, 2009. / Mode of access: Internet. Title from PDF title page; viewed on July 10, 2009. Major professor: Dr. Eric Mehiel. "Presented to the faculty of California Polytechnic State University at San Luis Obispo." "In partial fulfillment of the requirements for the degree [of] Master of Science in Aerospace Engineering with specialization in Space Systems Engineering." "April 2009." Includes bibliographical references (p. 48).

8 
Shielding characteristics of a commercial 19inch rackbased cabinetChen, Jue, January 2007 (has links) (PDF)
Thesis (M.S.)University of MissouriRolla, 2007. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed February 5, 2008) Includes bibliographical references (p. 82).

9 
Cable trays and EMC : modelling and measurementEbertsohn, Nolan Wade 12 1900 (has links)
Thesis (MScEng)University of Stellenbosch, 2005. / ENGLISH ABSTRACT: Common mode currents are a major source of interference in electrical and electronic
systems. A universal solution to counteract common mode interference is to introduce an
electromagnetic shield with known characteristics. Cable trays are often used to shield
cables from unwanted electromagnetic interference (EM!) and its shielding characteristics
are defined in terms of its transfer impedance. This thesis pursues the modelling and
measurement of the transfer impedance and mutual inductance of nonmagnetic cable
trays. Theoretical analysis is firstly employed by means of Maxwell's equations after
which method of moments (MoM) simulations are performed in order to determine the
transfer impedance and mutual inductance within the interior region of a cable tray. The
results obtained through simulation are then validated with measurements conducted with
an automatic network analyser (ANA). The computational and measured data are in good
agreement and the developed model can be used to predict the transfer impedance in the
crosssection of nonmagnetic cable trays. / AFRIKAANSE OPSOMMING: Gemenernodus strome is 'n bron van interferensie in elektriese en elektroniese stelsels. 'n
Universele oplossing om hierdie gemenernodus interferensie teen werk is om 'n
elektromagnetiese skerm met bekende eienskappe te implementeer. Geleier leikanale word
dikwels gebruik om kabels teen elektromagnetiese interferensie te beskerm en die
afskermings eienskappe word in terme van die kanaal se oordragsimpedansie gedefinieer.
Hierdie tesis ondersoek die modelering en meting van die wedersydse induktansie en
oordragsimpedansie van niemagnetiese geleier leikanale. 'n Teoretiese analise word eers
uitgevoer deur middel van Maxwell se vergelykings waarna metode van momente (MvM)
simulasies uitgevoer word om die oordragsimpedansie en wedersydse induktansie in die
interne gebied van 'n leikanaal te bepaal. Die resultate verkry deur simulasie word dan
bevestig deur meting wat uitgevoer word met behulp van 'n automatiese netwerk
analiseerder (ANA). Die numeriese en gemete data stem goed ooreen en die ontwikkelde
model kan deurgaans gebruik word om die oordragsimpedansie in die deursnit area van
niemagnetiese geleier leikanale te voorspel.

10 
Analysis of loss mechanisms in superconducting windings for rotating electric generatorsMinervini, Joseph Vito January 1981 (has links)
Thesis (Ph.D.)Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Vita. / Includes bibliographical references. / by Joseph Vito Minervini. / Ph.D.

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