Electrical and Electronics Commons^™

An Evaluation Of An Ada Implementation Of The Rete Algorithm For Embedded Flight Processors, F. Jesse Fanning

Theses and Dissertations

The purpose of this thesis was to design and develop an expert system shell in Ada, and to evaluate the shell's execution and size performance to determine its suitability for real-time operation on the MIL-STD-1750A embedded flight processor. The expert system shell uses the CLIPS/Ada inference engine, a forward-chaining Ada implementation of Rete. The expert system shell design is presented along with an overview of the target environment--the MIL-STD-1750A VHSIC Avionic Modular Processor (VAMP) running under the Ada Avionics Real-Time Software (AARTS) Operating System. Theoretical and empirical complexity analyses of the inference engine are presented and discussed in view of …

Deep Level Characterization Studies In Gaas, Gordhan R. Barevadia

Electrical & Computer Engineering Theses & Dissertations

The goal of this research was to investigate deep levels in different types of GaAs, a material for high power optically controlled bulk semiconductor switches. For low resistivity semiconductors, such as silicon doped GaAs material (p =0.054 Ω cm), deep level transient spectroscopy (DLTS) was used to characterize deep levels. Three deep levels (EL6, EL3, and EL2) have been detected in this material. For high resistivity semiconductors (p > 10⁴ Ω cm), difficulty of electrical carrier injection and of making a junction does not permit the use of DLTS technique. Therefore, an experimental set-up of the photo-induced current transient spectroscopy …

A Model Of Dc Glow Discharges With Abnormal Cathode Fall, Karl H. Schoenbach, Hao Chen, G. Schaefer

Bioelectrics Publications

A model for an abnormal glow discharge, including a self‐consistent analysis of the cathode fall, was developed. It combines microscopic particle simulation by means of Monte Carlo methods with a fluid model of the gas discharge. The model allows calculations of the steady‐state electrical field distribution, the charged‐particle densities, and the current densities along the axis of the discharge. The model was used to simulate a glow discharge in 80% He and 20% SF₆ at a pressure of 8 Torr with a current density of 1 A/cm². The computed discharge voltage agrees well with measured values. The …

Instrument Matrix Of The Four-Detector Photopolarimeter: Physical Meaning Of Its Rows And Columns And Constraints On Its Elements, R. M.A. Azzam

Electrical Engineering Faculty Publications

The four-detector photopolarimeter (FDP) is an arrangement of four photodetectors for measuring the state of polarization of light. The output current vector I of the FDP is related to the input Stokes vector S by I = AS, where A is the instrument matrix. The rows of A can be viewed as projection operators that determine the output currents of the detectors. This leads to the recognition of four special totally polarized input states, each of which maximizes the output of one detector. The associated four orthogonal states produce minimum signals. Because each detector is absorptive and its output is …

Accurate Calibration Of The Four-Detector Photopolarimeter With Imperfect Polarizing Optical Elements, R. M.A. Azzam, Ali G. Lopez

Electrical Engineering Faculty Publications

The first three columns of the instrument matrix A of the four-detector photopolarimeter (FDP) are determined by Fourier analysis of the output current vector I(P) as a function of the azimuth angle P of the incident linearly polarized light. Therefore 12 of the 16 elements of A are measured free of the imperfections of the (absent) quarter-wave retarder (QWR). The effect of angular beam deviation by the polarizer is compensated for by taking the average, (1/2) [I(P) + I(P + 180°)], of the FDP output at 180°-apart, optically equivalent, angular positions of the polarizer. The remaining fourth column of A …

Analytical Determination Of The Complex Dielectric Function Of An Absorbing Medium From Two Angles Of Incidence Of Minimum Parallel Reflectance, R. M.A. Azzam

Electrical Engineering Faculty Publications

The real and imaginary parts of the complex dielectric function (or complex refractive index) of an opaque substrate or a thick film can be determined from two pseudo-Brewster angles measured in two transparent incidence media of different refractive indices. This two-angle method is simple in that it involves no photometric or polarimetric analysis and in that the solution for the optical properties in terms of the measured angles is explicit, analytical, and direct (i.e. noniterative). The two-angle method is demonstrated for an opaque TiN film on a Cleartran ZnS substrate as a specific example. The effect of angle-of-incidence errors on …

Division-Of-Wave-Front Thin-Film Beam Splitter For Generating Binary Patterns Of Orthogonal Elliptical Polarization States, R. M.A. Azzam

Electrical Engineering Faculty Publications

A division-of-wave-front thin-film beam splitter is described that reflects monochromatic light at oblique incidence with orthogonal elliptical polarization states. It consists of a metallic substrate partially covered with a transparent thin film that inverts the ratio ρ of the complex p and s reflection coefficients at the principal angle of the metal. Any pattern of coated and uncoated areas of the substrate is imprinted upon the reflected wave front as a corresponding two-dimensional spatial binary polarization pattern. A specific design is given that uses a Au substrate at a wavelength of 632.8 nm. The effects of small errors in the …

Thin-Film Devices For Polarized Light- Introduction, R. M.A. Azzam, William H. Southwell

Electrical Engineering Faculty Publications

No abstract provided.

Extrema Of The Magnitude And The Phase Of A Complex Function Of A Real Variable: Application To Attenuated Internal Reflection, R. M.A. Azzam

Electrical Engineering Faculty Publications

Given a complex function F(ω) = |F(ω)|exp[jΔ(ω)] of a real argument ω, the extrema of its magnitude |F(ω)| and its phase Δ(ω), as functions of ω, are determined simultaneously by finding the roots of one common equation, Im[G(ω)] = 0, where G= (F′/F)² and F′ = ∂F/∂ω. The extrema of |F| and Δ are associated with Re G < 0 and Re G > 0, respectively. This easy-to-prove theorem has a wide range of applications in physical optics. We consider attenuated internal reflection (AIR) as …

General Analysis And Optimization Of The Four-Detector Photopolarimeter, R. M.A. Azzam, I. M. Elminyawi, A. M. El-Saba

Electrical Engineering Faculty Publications

The four-detector photopolarimeter (FDP) is analyzed for an arbitrary spatial configuration and any reflection characteristics (r_i, ψ_i, Δ_i) of the first three detectors. The instrument matrix A, which relates the output signal vector I to the input Stokes vector S by I = AS, and its determinant are derived explicitly. The essential condition that A be nonsingular (det A ≠ 0) is satisfied in general with uncoated absorbing detector surfaces, assuming that the plane of incidence (POI) is rotated between successive reflections by other than 90°. Therefore no special coatings on …

Model Of Hot-Film Sensor With Substrate Effects, David Mcalpine Judge

Electrical & Computer Engineering Theses & Dissertations

A detailed mathematical model is constructed to investigate the frequency response of a hot-film anemometer system. Since several diverse factors affect the frequency response, the analysis is broken down into three main parts. Each part is a detailed mathematical model. The first model consists of the ordinary differential equations which govern the electronics of the feedback system and heat transfer of the sensor. An important simplification in this model is that the rate of heat conduction from the sensor to its substrate is constant.

In the second model the unsteady state heat transfer properties of the substrate are examined by …

Antireflection Of An Absorbing Substrate By An Absorbing Thin Film At Normal Incidence, R. M.A. Azzam, E. Bu-Habib, J. Casset, G. Chassaing, P. Gravier

Electrical Engineering Faculty Publications

An absorbing substrate of complex refractive index n₂ - jk₂ at wavelength λ can be coated by an absorbing thin film of complex refractive index n₁ - jk₁ and thickness d to achieve zero reflection at normal incidence. For given n₂,k₂ multiple solutions (n₁,k₁,d/λ) are found that correspond to infinitely many distinct antireflection layers. This is demonstrated for a Si substrate at two wavelengths (6328 and 4420 Å). The response of these absorbing antireflection layers to changes of the angle of incidence from 0 …

Polarizing Beam Splitters For Infrared And Millimeter Waves Using Single-Layer-Coated Dielectric Slab Or Unbacked Films, R. M.A. Azzam

Electrical Engineering Faculty Publications

No abstract provided.

Thin-Film Beam Splitter That Reflects Light As A Half-Wave Retarder And Transmits It Without Change Of Polarization: Application To A Michelson Interferometer, R. M.A. Azzam

Electrical Engineering Faculty Publications

The refractive index n₁ of a transparent layer of quarter-wave optical thickness coating a transparent substrate of refractive index n₂ can be chosen to produce half-wave retardation (HWR) in reflection and no change of polarization in refraction at any angle of incidence ø. The function n₁(ø, n₂), and the associated polarization-independent reflectance of the film-substrate system R(ø, n₂) are determined. Such a coated surface can be used as a beam splitter with excellent characteristics (e.g., split fractions that do not depend on source polarization, a split beam whose polarization is identical …

Relationship Between The P And S Fresnel Reflection Coefficients Of An Interface Independent Of Angle Of Incidence, R. M.A. Azzam

Electrical Engineering Faculty Publications

The Fresnel reflection coefficients r_p and r_s of p- and s-polarized light at the planar interface between two linear isotropic media are found to be interrelated by (r_s - r_p)/(1 - r_sr_p) = cos 2β, independent of the angle of incidence ø, where tan²β = ∊ and ∊ is the (generally complex) ratio of dielectric constants of the media of refraction and incidence. This complements another relation (found earlier), (r²_s - r_p)/(r_s - r_sr_p) = …

Total Refraction At Oblique Incidence By A Transparent Bilayer Coating On A High-Index Transparent Or Absorbing Substrate, R. M.A. Azzam, Karim Javily

Electrical Engineering Faculty Publications

Transparent bilayer coatings that produce total refraction (TR) of obliquely incident monochromatic light into an underlying substrate are considered. When the substrate is transparent, it is shown that TR takes place without any accompanying change of polarization. Totally refracting bilayers are realizable in the IR where high-refractive-index substrates are available. This is illustrated by a BaF₂–ZnSe bilayer on a Ge substrate at a 10.6-μm (CO₂-laser) wavelength and 45° angle of incidence. Limited changes of the angle of incidence, wavelength, and refractive indices and thicknesses of the two films of the bilayer are introduced, and their effects …

Investigation Of Electronic Holography Using Spice Computer Simulation Experiments, Monish Ranjan Chatterjee

Electrical and Computer Engineering Faculty Publications

Using SPICE experiments, it has been possible to verify most of the important aspects of electronic holography. The generation and properties of dynamic echoes under different types of nonlinearities have been extensively tested, and some new information has been garnered in the process. The case of pulse and generalized memory echoes has also been tested, and the results have been fairly satisfactory. Most of all, the simplicity with which the intriguing concept of memory echoes has translated into the circuit implementation on SPICE, and the closeness of the results to predicted behavior have been somewhat of a pleasant surprise.

Since …

Constraint On The Optical Constants Of A Film-Substrate System For Operation As An External-Reflection Retarder At A Given Angle Of Incidence, R. M.A. Azzam, Bruce E. Perilloux

Electrical Engineering Faculty Publications

Given a transparent film of refractive index n₁ on an absorbing substrate of complex refractive indexn₂-jk₂, we examine the constraint on n₁, n₂, and k₂ such that the film-substrate system acts as an external-reflection retarder of specified retardance Δ at a specified angle of incidence φ. The constraint, which takes the form ƒ(n₁,n₂,k₂;φ,Δ) = 0, is portrayed graphically by equi-n₁ contours in the n₂,k₂ plane at φ = 45, 70° and for Δ …

Explicit Equations For The Polarizing Angles Of A High-Reflectance Substrate Coated By A Transparent Thin Film, R. M.A. Azzam

Electrical Engineering Faculty Publications

Simple explicit equations are derived that determine the angles of incidence at which the parallel and perpendicular polarization components of light are extinguished on reflection from a transparent film coating a high-reflectance (metallic) substrate. The polarizing angles obtained from our approximate expressions are in excellent agreement with those determined by iterative numerical solution of the exact nonlinear equations that govern such angles. For the approximation to be valid, the intensity reflectance of the film-substrate interface, evaluated at the critical angle of the film-ambient interface, must exceed 0.5.

Antireflecting And Polarizing Transparent Bilayer Coatings On Absorbing Substrates At Oblique Incidence, R. M.A. Azzam, Karim Javily

Electrical Engineering Faculty Publications

The condition of zero reflection of p- and s-polarized light by a transparent bilayer on an absorbing substrate is derived in the form |g_ν(ø,N_i)| ≤ 1, where g_ν is a function of the angle of incidence ø, the refractive indices N_i(i = 0,1,2,3) of the system, and the polarization state ν (= p or s). As an application, the air-Si₃N₄-SiO₂-Si system is considered at two laser wavelengths λ = 6328 and 3250 Å. The thicknesses of the two films of the bilayer and the …

Single-Layer Antireflection Coatings On Absorbing Substrates For The Parallel And Perpendicular Polarizations At Oblique Incidence, R. M.A. Azzam

Electrical Engineering Faculty Publications

Explicit equations are derived that determine the refractive index of a single layer that suppresses the reflection of p- or s-polarized light from the planar interface between a transparent and an absorbing medium at any given angle of incidence. The required layer thickness and the system reflectance for the orthogonal unextinguished polarization also follow explicitly. This generalizes earlier work that was limited to normal incidence or to oblique incidence at dielectric—dielectric interfaces. Specific examples are given of p- and s-antireflection layers on Si and Al substrates at λ = 6328 Å at various angles of incidence.

Extinction Of The P And S Polarizations Of A Wave On Reflection At The Same Angle From A Transparent Film On An Absorbing Substrate: Applications To Parallel-Mirror Crossed Polarizers And A Novel Integrated Polarimeter, R. M.A. Azzam

Electrical Engineering Faculty Publications

The p- and s-polarized components of light can be suppressed on reflection at the same angle of incidence from an absorbing substrate coated by a transparent thin film if the wave is refracted in the film at 45° and the constraint Re[(ε₂ - α)/(l -α)]^1/2 = α + | ε₂ - α| is satisfied, where 2α and ε₂ are the ratios of dielectric constants of the film and substrate, respectively, to that of the ambient. For high-reflectance metal substrates (|ε₂| » 1), α≈ 1, the ratio of film to ambient refractive index …

Multiple Determination Of The Optical Constants Of Thin-Film Coating Materials, D. P. Arndt, R. M.A. Azzam, J. M. Bennett, J. P. Borgogno, C. K. Carniglia, W. E. Case, J. A. Dobrowolski, U. J. Gibson, T. Tuttle Hart, F. C. Ho, V. A. Hodgkin, W. P. Klapp, H. A. Macleod, E. Pelletier, M. K. Purvis, D. M. Quinn, D. H. Strome, R. Swenson, P. A. Temple, T. F. Thonn

Electrical Engineering Faculty Publications

The seven participating laboratories received films of two different thicknesses of Sc₂O₃ and Rh. All samples of each material were prepared in a single deposition run. Brief descriptions are given of the various methods used for determination of the optical constants of these coating materials. The measurement data are presented, and the results are compared. The mean of the variances of the Sc₂O₃refractive-index determinations in the 0.40–0.75-nm spectral region was 0.03. The corresponding variances for the refractive index and absorption coefficient of Rh were 0.35 and 0.26, respectively.

Three-Reflection Halfwave And Quarterwave Retarders Using Dielectric-Coated Metallic Mirrors, T. F. Thonn, R. M.A. Azzam

Electrical Engineering Faculty Publications

A design procedure is described to determine the thicknesses of single-layer coatings of a given dielectric on a given metallic substrate so that a specified net phase retardance (and/or a net relative amplitude attenuation) between the p and s polarizations is achieved after three reflections from a symmetrical arrangement of three mirrors that maintain collinearity of the input and output beams. Examples are presented of halfwave and quarterwave retarders (HWR and QWR) that use a ZnS-Ag film-substrate system at the CO₂-laser wavelength λ = 10.6 µm. The equal net reflectances for the p and s polarizations are computed …

Inverting The Ratio Of The Complex Parallel And Perpendicular Reflection Coefficients Of An Absorbing Substrate Using A Transparent Thin-Film Coating, R. M.A. Azzam

Electrical Engineering Faculty Publications

An absorbing substrate can be coated with a transparent thin film of refractive index N₁ (within a certain range) and thickness d such that the ratio of complex reflection coefficients for the p_and s polarizations of the film-covered substrate ρ = R_p/R_s is the inverse of that of the film-free substrate ρ¯ = R¯_p/R¯_s at an angle of incidence ø. A method to determine the relationship among ø, N₁, and d that inverts ρ (i.e., makes ρ = 1/ρ¯) for a given substrate at a given wavelength is described and is …

Division-Of-Wave-Front Polarizing Beam Splitter And Half-Shade Device Using Dielectric Thin Film On Dielectric Substrate, R. M.A. Azzam

Electrical Engineering Faculty Publications

No abstract provided.

A Plasma Focus Interrupting Switch, Gregory Francis Knapp

Electrical & Computer Engineering Theses & Dissertations

The feasibility of using a dense plasma focus (DPF) as a current interrupting device has been investigated. Specifically, a 34-kJ, Mather-type DPF was modified to accept a third electrode so that a discharge could be created between this electrode and the center electrode of the DPF by a 10-kJ inductive energy storage circuit. It was anticipated that the accelerating mechanisms of the DPF pinch, which are known to cause a rapid reduction in the DPF current, would interrupt the 1-kA to 10-kA secondary discharge current thus forcing the secondary current through an external load and hence result in power amplification. …

Pseudo-Brewster And Second-Brewster Angles Of An Absorbing Substrate Coated By A Transparent Thin Film, R. M.A. Azzam, T F. Thonn

Electrical Engineering Faculty Publications

The pseudo-Brewster angle of minimum reflectance for the p polarization, the corresponding angle for thes polarization, and the second-Brewster angle of minimum ratio of the p and s reflectances are all determined as functions of the thickness of a transparent film coating an absorbing substrate by numerical solution of the exact equations that govern such angles of the form Re(Z′/Z) = 0, where Z = R_p, R_s, or ρ represent the complex amplitude-reflection coefficients for the p and s polarizations and their ratio (ρ =R_p/R_s), …

Self‐Refraction Of Nonlinear Capillary‐Gravity Waves, Partha P. Banerjee, Adrianus Korpel, Karl E. Lonngren

Electrical and Computer Engineering Faculty Publications

Self‐refraction effects have been observed during the propagation of deep‐water capillary‐gravity waves. The observations are shown to be in qualitative agreement with the theory of self‐focusing and defocusing in a cubically nonlinear medium in the presence of diffraction.

Explicit Equations For The Second Brewster Angle Of An Interface Between A Transparent And An Absorbing Medium, R. M.A. Azzam

Electrical Engineering Faculty Publications

The second Brewster angle _ΦB2, at which the ratio R_p/R_s of intensity reflectances R_p and R_s for the parallel (p) and the perpendicular (s) polarizations of a dielectric-conductor interface reaches a minimum, is determined by Im[(u - ∊)(u - ∊)²/(u - 2∊)²] = 0, where ∊ is the complex ratio of dielectric constants of the media of refraction and incidence, ∊ = ∊/(∊ + 1), and u= sin²_ΦB2. An equivalent quartic equation in u …