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Electrical and Computer Engineering

1994

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Articles 1 - 30 of 90

Full-Text Articles in Engineering

United States Patent: Ellipsometer, John A. Woollam, Blaine D. Johs, David W. Doerr, Reed A. Christenson Dec 1994

United States Patent: Ellipsometer, John A. Woollam, Blaine D. Johs, David W. Doerr, Reed A. Christenson

Department of Electrical and Computer Engineering: Faculty Publications

To sense characteristics of a sample, an ellipsometer includes a pivotal diffraction grating positioned to receive white light from the analyzer without further focusing of the light after the light leaves the sample. The diffraction grating is focused on the sensor at a predetermined angle with a precision of at least plus or minus one-half degree using an alignment-sensing means positioned between the analyzer and diffraction grating. The sensor includes an aperture through which the incident beam of light is transmitted, light-sensitive areas on opposite sides of said sensor and a comparator for comparing the signal from said light-sensitive areas. …

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Travelling Wave Electrode Optimization For High Speed Electro-Optic Modulators Using The Fourier Series Method, W. Boyu, X. Guangjun, Xiaomin Jin Dec 1994

Travelling Wave Electrode Optimization For High Speed Electro-Optic Modulators Using The Fourier Series Method, W. Boyu, X. Guangjun, Xiaomin Jin

Electrical Engineering

The performance of Z-cut Mach-Zehnder high speed LiNbO3 amplitude modulators with a CPW traveling wave electrode, has been analyzed and optimally designed in detail by the Fourier series method. The effect of electrode and buffer layer thickness on the electric field distribution in the substract, effective micro- wave refractive index and characteristic impedance of CPW electrode, are discussed. Calculation shows that increasing the thickness of the electrode and SiO2 buffer layer can improve the phase velocity mismatch between electric and optical waves, and the drive power required by the modulator with thin buffer layer and thick electrode is …

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Instability In Self-Pulsation In Laser Diodes And Its Effect On All-Optical Synchonization, Jonathan Hyland, Gerald Farrell Dec 1994

Instability In Self-Pulsation In Laser Diodes And Its Effect On All-Optical Synchonization, Jonathan Hyland, Gerald Farrell

Articles

The effect of short- and long-term frequency instability in self pulsation on all-optical synchronization using a twin-section laser diode is experimentally investigated. Short-term frequency instability broadens the unlocked full width at half maximum (FWHM) of the fundamental of the rf spectrum of the self-pulsating laser diode. We show experimentally that the value of the unlocked FWHM, and thus the level of short-term instability, has a direct effect on the optical power required to maintain synchronization. A novel means of reducing the FWHM is presented based on a reflective transmission line stub connected to the absorber of the twin-section self-pulsating laser …

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An Overview Of Flexible Ac Transmission Systems, P. Asare, T. Diez, A. Galli, E. O'Neill-Carillo, J. Robertson, R. Zhao Dec 1994

An Overview Of Flexible Ac Transmission Systems, P. Asare, T. Diez, A. Galli, E. O'Neill-Carillo, J. Robertson, R. Zhao

Department of Electrical and Computer Engineering Technical Reports

FACTS or "flexible AC transmission systems" is a term that has been suggested for the use of solid state devices to control bulk power flow in transmission systems. The Electric Power Research Institute supported this idea, and many researchers have invested efforts on the value and potential of FACTS. At this time, it appears that the main value of FACTS lies in improving transmission capability; increasing the flexibility of power flow control (e.g., for wheeling or for economic dispatch); for controlling voltage (and var flow); and possibly additional advantages in lower voltage systems (e.g., distribution systems). This report is an …

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A Contactless Method For Measuring The Bulk Resistance Of Ii-Vi Compound Semiconductors, Edward D. Wheeler, Jack L. Boone, James L. Drewniak Dec 1994

A Contactless Method For Measuring The Bulk Resistance Of Ii-Vi Compound Semiconductors, Edward D. Wheeler, Jack L. Boone, James L. Drewniak

Electrical and Computer Engineering Faculty Research & Creative Works

A radio frequency measurement technique for measuring the bulk resistivity of II-VI compound semiconductors is described. Wafers of n-type CdS are used to demonstrate the technique. An equivalent circuit model is introduced which predicts a frequency dependence for the CdS wafer impedance which agrees well with the experiment. The model assumes a broad distribution of relaxation times associated with the polarization. The radio frequency method gives values for the resistivity within 15% of four point probe measurements for the lower resistivity wafers, and within 5% for the higher resistivity wafers.

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The Fat-Pyramid And Universal Parallel Computation Independent Of Wire Delay, Ronald I. Greenberg Dec 1994

The Fat-Pyramid And Universal Parallel Computation Independent Of Wire Delay, Ronald I. Greenberg

Computer Science: Faculty Publications and Other Works

This paper shows that a fat-pyramid of area Θ(A) requires only O(log A) slowdown to simulate any competing network of area A under very general conditions. The result holds regardless of the processor size (amount of attached memory) and number of processors in the competing networks as long as the limitation on total area is met. Furthermore, the result is valid regardless of the relationship between wire length and wire delay. We especially focus on elimination of the common simplifying assumption that unit time suffices to traverse a wire regardless of its length, since the assumption becomes more and more …

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Optical-Fiber Preamplifiers For Ladar Detection And Associated Measurements For Improving The Signal-To-Noise Ratio, Michael S. Salisbury, Paul F. Mcmanamon, Bradley D. Duncan Dec 1994

Optical-Fiber Preamplifiers For Ladar Detection And Associated Measurements For Improving The Signal-To-Noise Ratio, Michael S. Salisbury, Paul F. Mcmanamon, Bradley D. Duncan

Electro-Optics and Photonics Faculty Publications

In an effort to increase achievable postdetection signal-tonoise ratios (SNRs) of continuous-wave, 1-gm all-solid-state ladar systems, a prototype rare-earth-doped optical-fiber amplifier has been included in the optical return signal path of both a heterodyne and a directdetection ladar system. We provide numerical predictions for SNR increases according to our previously developed theory. We also detail our experimental efforts and provide the results of SNR measurements for four distinct cases: direct ladar detection with and without a fiber amplifier, and heterodyne ladar detection with and without a fiber amplifier. Experimentally measured increases in SNRs for ladar systems incorporating an optical-fiber amplifier …

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Broadband Rf Current Detector, George Cabrera Nov 1994

Broadband Rf Current Detector, George Cabrera

FIU Electronic Theses and Dissertations

The problems to be solved in this thesis were 1) development of a broadband RF preamplifier to be used with non-ferrous current probes so that the amplified signal exceeds the errors due to cable pickup, no detection is needed in this application, and 2) development of a self-contained device that amplifies and detects the output from a nonferrous current probe, providing a digital readout of the current. These instruments have been completed and are being tested for use by the National Institutes of Occupational Safety and Health (NIOSH). The self-contained current meter operates at frequencies up to 600 MHz, and …

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Performance Of Bandlimited Gaussian Noise As A Spreading Code In Awgn And Single Tone Interference Channels, Tze-Yu Chu, Kurt Louis Kosbar Nov 1994

Performance Of Bandlimited Gaussian Noise As A Spreading Code In Awgn And Single Tone Interference Channels, Tze-Yu Chu, Kurt Louis Kosbar

Electrical and Computer Engineering Faculty Research & Creative Works

This paper examines the bit error rate (BER) of a direct sequence spread spectrum (SS) system that uses bandlimited white Gaussian noise (BLWGN) as a spreading code. The performance of this "bandlimited-SS" system is examined in both additive white Gaussian noise (AWGN) and single tone jamming environments. The BLWGN spreading code is inferior to conventional codes in AWGN channels, but is more robust when a narrow band interference signal is present.

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Beam Propagation In Parabolically Tapered Graded-Index Waveguides, Anthony A. Tovar, Lee W. Casperson Nov 1994

Beam Propagation In Parabolically Tapered Graded-Index Waveguides, Anthony A. Tovar, Lee W. Casperson

Electrical and Computer Engineering Faculty Publications and Presentations

To a good approximation, the electromagnetic-propagation characteristics of graded-index waveguides can be written in terms of polynomial-Gaussian modes. For uniform quadratic-index waveguides the behavior of these modes is well known. However, there are sometimes practical reasons for using tapered waveguides, but detailed propagation solutions are known for only a few specific taper functions. The parabolic taper is perhaps the most important special case, and the solution-generating techniques that we generalize are used to obtain analytic solutions for this case.

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Correlative Tracking Of Pseudo-Noise Codes Using A Phase Shifted Reference, Kurt Louis Kosbar, Hettiachchi Upul Gunawardana Nov 1994

Correlative Tracking Of Pseudo-Noise Codes Using A Phase Shifted Reference, Kurt Louis Kosbar, Hettiachchi Upul Gunawardana

Electrical and Computer Engineering Faculty Research & Creative Works

This work investigates a first-order correlation loop for tracking pseudo-noise (PN) codes. The local reference is produced by a PN sequence generator in series with a Hilbert transform filter. The tracking performance of this non-linear loop is compared with conventional early-late delay-lock loops (ELDLL). Using a conservative definition of bandwidth, the new loop was found to be superior at moderate to low signal-to-noise ratios (SNR). Another advantage of the new structure is that it has a very large (arguably infinite) lock range.

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Two-Dimensional Current Transient And Trap-State Filling Of Amorphous Silicon Thin-Film Transistors, J. S. Huang, Cheng-Hsiao Wu Nov 1994

Two-Dimensional Current Transient And Trap-State Filling Of Amorphous Silicon Thin-Film Transistors, J. S. Huang, Cheng-Hsiao Wu

Electrical and Computer Engineering Faculty Research & Creative Works

Two-dimensional simulations of amorphous silicon thin-film transistors are presented for the case when source-drain voltage is turned on long before gate voltage is turned on. Discrepancies between these results and the one-dimensional results of M. F. Willums, M. Hack, P. G. LeComber, and J. G. Shaw [MRS Symp. Proc. 258, 985 (1992)] are discussed. Valid reasons for drain current decay are provided, and occupation dynamics for the trap states are shown in order to distinguish these from the one-dimensional results of C. van Berkel, J. R. Hughes, and M. J. Powell [J. Appl. Phys. 66, 4488 (1989)] where …

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Low Cost Schottky Barrier Solar Cells Fabricated On Cdse And Sb2S3 Films Chemically Deposited With Silicotungstic Acid, O. Savadogo, K. C. Mandal Oct 1994

Low Cost Schottky Barrier Solar Cells Fabricated On Cdse And Sb2S3 Films Chemically Deposited With Silicotungstic Acid, O. Savadogo, K. C. Mandal

Faculty Publications

No abstract provided.

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A Novel Microwave Method For Detection Of Long Surface Cracks In Metals, Chin-Yung Yeh, R. Zoughi Oct 1994

A Novel Microwave Method For Detection Of Long Surface Cracks In Metals, Chin-Yung Yeh, R. Zoughi

Electrical and Computer Engineering Faculty Research & Creative Works

A novel microwave technique for detecting long surface cracks in metals is described. This technique utilizes an open-ended waveguide to probe the surface of a metal. In the absence of a crack the metal surface is seen as a relatively good short-circuit load. However, in the presence of a crack higher order modes are generated which in turn change the reflection properties at the waveguide aperture. This change brings about a perturbation in the standing wave characteristics which is then probed by a diode detector. The experimental and theoretical foundations of this technique are given, along with several examples. It …

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Generalized Reverse Theorems For Multipass Applications In Matrix Optics, Lee W. Casperson, Anthony A. Tovar Oct 1994

Generalized Reverse Theorems For Multipass Applications In Matrix Optics, Lee W. Casperson, Anthony A. Tovar

Electrical and Computer Engineering Faculty Publications and Presentations

The reverse theorem that governs backward propagation through optical systems represented by transfer matrices is examined for various matrix theories. We extend several reverse theorems to allow for optical systems represented by matrices that may or may not be unimodular and that may be 2 × 2 or take on an augmented 3 × 3 form. As an example, we use the 3 × 3 form of the reverse theorem to study a laser with intracavity misaligned optics. It is shown that, by tilting one of the laser's mirrors, we can align the laser output arbitrarily, and the mirror tilt …

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Complex Index-Of-Refraction Measurements For Rp-1 Liquid Rocket Fuel, Dennis R. Alexander, Ramu Kaiwala, Robert D. Kubik, Scott A. Schaub Sep 1994

Complex Index-Of-Refraction Measurements For Rp-1 Liquid Rocket Fuel, Dennis R. Alexander, Ramu Kaiwala, Robert D. Kubik, Scott A. Schaub

Department of Electrical and Computer Engineering: Faculty Publications

Complex index-of-refraction values of RP-1 liquid rocket fuel are reported at laser wavelengths of 0.193 m (ArF excimer), 0.4765 m (argon ion), 0.488 im (argon ion), 0.5145 ji.m (argon ion), 0.532 m (Nd-YAG, frequency doubled), 0.6328 pm (He-Ne), 1 .064 im (Nd-YAG), and 10.5915 im (C02). The imaginary part of the index of refraction (k) is determined by traditional transmission methods. The real part (flr) at the specific laser lines is determined using reflectance measurements, critical-angle measurements, Mueller matrix elements, and Michelson interferometric measurements. Reflectance measurements are used to obtam n at a wavelength of 0.193 m. The critical-angle method …

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Polarized Light Reflectometer, R. M.A. Azzam Sep 1994

Polarized Light Reflectometer, R. M.A. Azzam

Electrical Engineering Faculty Publications

The modulated reflected and nonreflected light fluxes, measured as the azimuth of incident linearly polarized light is varied, yield the absolute reflectances Rp, and Rs, of a dielectric or semiconductor surface. Application to a reflective Si detector determines the refractive index and thickness of a SiO2 film on the detector surface.

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The Impact Of Electronic Ballast Compact Fluorescent Lighting On Power Distribution Systems, Reid Iwao Sasaki Sep 1994

The Impact Of Electronic Ballast Compact Fluorescent Lighting On Power Distribution Systems, Reid Iwao Sasaki

Department of Electrical and Computer Engineering Technical Reports

Due to the high costs of expanding generation and transmission capacities, utilities have been initiating programs to reduce peak power demand by the customer. A number of these programs, which are commonly referred to as demand side management programs, have turned to the promotion of electronic ballast compact fluorescent lamps (CFLs) as an alternative to traditional incandescent lamps. These lamps provide a higher luminance and increased life as compared to their incandescent counterparts. Unfortunately, electronic ballast CFLs consume large amounts of harmonic current which may prove detrimental to the power distribution system. This thesis presents an introduction to the electronic …

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An Appraisal Of Electricity Supply In Nigeria And The Privatisation Option, E. I. K. Sule, C. M. Anyanwu Aug 1994

An Appraisal Of Electricity Supply In Nigeria And The Privatisation Option, E. I. K. Sule, C. M. Anyanwu

CBN Occasional Papers

Incessant electric power cuts in most parts of the country has become a normal feature of electricity supply throughout Nigeria. The power outages cause much inconvenience and economic losses to all and sundry. This study has shown that the most critical factor behind the incessant power failure is the problem of inadequate funding of the industry at a time it was forced to accommodate rapid expansion. Other factors include lack of autonomy, inefficiency, poor organization as well as lack of skilled manpower. The paper has examined these problems on the basis of which suggestions are made on how the worrisome …

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Diffraction Grating Photopolarimeters And Spectrophotopolarimeters, Rasheed M.A. Azzam Aug 1994

Diffraction Grating Photopolarimeters And Spectrophotopolarimeters, Rasheed M.A. Azzam

University of New Orleans Patents

A division-of-amplitude photopolarimeter based on conical grating diffraction includes a diffraction grating and at least four photodetectors. An incident light beam is directed at the grating at an oblique incidence angle

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Identifying And Quantifying Printed Circuit Board Inductance, Todd H. Hubing, Thomas Van Doren, James L. Drewniak Aug 1994

Identifying And Quantifying Printed Circuit Board Inductance, Todd H. Hubing, Thomas Van Doren, James L. Drewniak

Electrical and Computer Engineering Faculty Research & Creative Works

The concepts of inductance and partial inductance play a key role in printed circuit board (PCB) modeling. The inductance of the signal path is an important parameter in high-speed signal integrity calculations. Delta_I noise modeling, crosstalk calculations, and common-mode source identification all rely heavily on accurate estimations of the partial inductance associated with traces, vias, and signal return paths on printed circuit boards. The paper begins by identifying and quantifying the parameters that affect the inductance of typical PCB geometries. Closed-form equations are provided for estimating the partial inductances of simple trace, via, and ground plane configurations. Finally, the issue …

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Modeling Power Bus Decoupling On Multilayer Printed Circuit Boards, James L. Drewniak, Todd H. Hubing, Thomas Van Doren, P. Baudendistal Aug 1994

Modeling Power Bus Decoupling On Multilayer Printed Circuit Boards, James L. Drewniak, Todd H. Hubing, Thomas Van Doren, P. Baudendistal

Electrical and Computer Engineering Faculty Research & Creative Works

Power bus decoupling designs on multilayer printed circuit boards must adequately account for the power bus interplane capacitance and its consequences for the design. Lumped element models for a power bus on a multilayer printed circuit board where an appreciable or entire portion of a layer is devoted to power and ground have been developed. The models are applicable below the distributed resonances of the board. Analytical, circuit simulation, and experimental studies have been conducted to test the models, investigate the effects of the distributed interplane capacitance of the power bus, and the effect of interconnect inductance associated with surface-mount …

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Common Mode Currents Induced On Wires Attached To Multilayer Printed Wire Boards With Segmented Ground Planes, R. Lee Hill, Thomas Van Doren, Todd H. Hubing, James L. Drewniak, Franz Gisn Aug 1994

Common Mode Currents Induced On Wires Attached To Multilayer Printed Wire Boards With Segmented Ground Planes, R. Lee Hill, Thomas Van Doren, Todd H. Hubing, James L. Drewniak, Franz Gisn

Electrical and Computer Engineering Faculty Research & Creative Works

An investigation has been undertaken to further study the fundamental mechanisms responsible for inducing high frequency common mode currents on wires attached to multilayer printed wire boards (PWBs). Previous work reported in the EMC literature has demonstrated that the presence of unintended common mode currents on the external cables of electronic equipment is often the primary source of radiated EMI at frequencies above 30 MHz. In an attempt to reduce the magnitude of these currents to yield `quieter' electronic products, many EMC engineers have implemented segmented or `gapped' ground plane geometries in mulilayer PWB designs. The objective of this study …

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The Multirate Method For Simulation Of Power System Dynamics, J. G. Chen, Mariesa Crow Aug 1994

The Multirate Method For Simulation Of Power System Dynamics, J. G. Chen, Mariesa Crow

Electrical and Computer Engineering Faculty Research & Creative Works

In this paper, the multirate method is introduced to analyse power system behavior for systems with widely varying time constants. Estimates for computational speed-up are derived based on a linear system approach. The method is applied to a small power system example and the results, both in terms of accuracy and computation time, are compared to traditional simulation methods

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Performance Analysis Of Antennas For Hand-Held Transceivers Using Fdtd, Michael A. Jensen, Yahya Rahmat-Samii Aug 1994

Performance Analysis Of Antennas For Hand-Held Transceivers Using Fdtd, Michael A. Jensen, Yahya Rahmat-Samii

Faculty Publications

The design of antennas for hand-held communications devices depends on the implementation of simulation tools that can accurately model general topologies. The paper presents the analysis of small antennas mounted on hand-held transceivers using the finite-difference time-domain (FDTD) method. The key features of the FDTD implementation are discussed, with particular emphasis placed upon modeling of the source region. The technique is used to predict the gain patterns and broadband input impedance behavior of monopole, planar inverted F, and loop antenna elements mounted on the handset. Effects of the conducting handset chassis, the plastic casing around the device, and lumped elements …

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Investigation Of Fundamental Mechanisms Of Common-Mode Radiation From Printed Circuit Boards With Attached Cables, James L. Drewniak, Todd H. Hubing, Thomas Van Doren Aug 1994

Investigation Of Fundamental Mechanisms Of Common-Mode Radiation From Printed Circuit Boards With Attached Cables, James L. Drewniak, Todd H. Hubing, Thomas Van Doren

Electrical and Computer Engineering Faculty Research & Creative Works

Fundamental mechanisms leading to common-mode radiation from printed circuit boards with attached cables have been studied. Two primary mechanisms have been identified, one associated with a differential-mode voltage that results in a common-mode current on an attached cable, and another associated with a differential-mode current that results in a common-mode current on the cable. The two mechanisms are demonstrated through numerical and experimental results.

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Schottky Effect At A Metal-Polymer Interface, G. Rikken, David Braun, E. Staring, R. Demandt Jul 1994

Schottky Effect At A Metal-Polymer Interface, G. Rikken, David Braun, E. Staring, R. Demandt

Electrical Engineering

We report the observation of the Schottky effect at the interface between a metal and a semiconducting polymer by means of internal photoemission spectroscopy. The bias dependence of the barrier provides information on the electrical properties of the polymer.

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Gradient Based Fuzzy C-Means Algorithm, Issam J. Dagher Jul 1994

Gradient Based Fuzzy C-Means Algorithm, Issam J. Dagher

FIU Electronic Theses and Dissertations

A clustering algorithm based on the Fuzzy c-means algorithm (FCM) and the gradient descent method is presented. In the FCM, the minimization process of the objective function is proceeded by solving two equations alternatively in an iterative fashion. Each iteration requires the use of all the data at once. In our proposed approach one datum is presented at a time to the network and the minimization is proceeded using the gradient descent method. Compared to FCM, the experimental results show that our algorithm is very competitive in terms of speed and stability of convergence for large number of data.

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State-Of-The-Art: In Polymer Light-Emitting Diodes Neome Polymer Led Mini Symposium (15–17 September 1993, Eindhoven, The Netherlands), David Braun, Adam Brown, Emiel Staring, E. W. Meijer Jul 1994

State-Of-The-Art: In Polymer Light-Emitting Diodes Neome Polymer Led Mini Symposium (15–17 September 1993, Eindhoven, The Netherlands), David Braun, Adam Brown, Emiel Staring, E. W. Meijer

Electrical Engineering

A symposium focused on recent progress in the field of polymer light-emitting diodes was held in Eindhoven during the period 15–17 September 1993. The following is a brief summary of highlights of the symposium. There will be no published proceedings.

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Direct Relation Between Fresnel's Interface Reflection Coefficients For The Parallel And Perpendicular Polarizations: Erratum 2, R. M.A. Azzam Jul 1994

Direct Relation Between Fresnel's Interface Reflection Coefficients For The Parallel And Perpendicular Polarizations: Erratum 2, R. M.A. Azzam

Electrical Engineering Faculty Publications

The record is set straight concerning two equations that determine the reflection phase shifts at a single interface from the intensity reflectances forp- and s-polarized light at one angle of incidence. These equations appeared previously in this journal [J. Opt. Soc. Am. 69, 1007 (1979); erratum, J. Opt. Soc. Am. 70, 261 (1980)].

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