Engineering Commons^™

Liquid Transmission Line Pulser Circuit For Laser Excitation, Carl Stultz

Dissertations and Theses

The subject of this thesis is the study of liquid dielectric transmission lines and their potential application as an excitation source in high speed, high-repetition rate laser designs. The design problems associated with the construction of high repetition rate (khz), short wavelength lasers have been reviewed and the major shortcomings of conventional electrical driving circuits identified. The identification of these shortcomings and a review of the available literature on electrical circuits for various types of lasers suggested that liquid dielectrics and transmission lines could potentially have significant advantages over more conventional circuitry used in high repetition rate, short wavelength lasers. …

Radio-Frequency-Excited Carbon Dioxide Metal Waveguide Laser, Jonathan Gary Grossman, Lee W. Casperson, O. M. Stafsudd

Electrical and Computer Engineering Faculty Publications and Presentations

A new type of waveguide laser is described in which a single-surface concave metal waveguide also doubles as the grounded electrode in a radio-frequency-excited gaseous discharge. The laser’s output modes and spectrum have been studied theoretically and experimentally for cw CO₂ operation of the laser. Overall operating efficiency and mode stability are comparable with those of conventional dielectric waveguide CO₂ lasers, and advantages of the metal waveguide laser include convection cooling, intracavity mode control, and partial self-alignment.

Analytical And Experimental Stresses In Concrete Pavements And Unbonded Overlays, Ahmad Jaber

Dissertations and Theses

The principal objective of this study is to determine the accuracy of calculating stresses in concrete pavements and unbonded overlays under different loading conditions. The computed stresses for the single layer pavements are obtained based on Westergaard theory, the finite-element model (ILLI-SLAB), and the elastic layered model (ELSYM5). For the two-layer unbonded systems, stresses are estimated based on the finite-element theory and the Portland Cement Association design method. The experimental results for the comparison were available from a series of tests done on model scale concrete pavements and unbonded overlays. The results of present investigation show that the computed stresses …

Secondary Stresses In Bowstring Timber Trusses, John F. Bradford

Dissertations and Theses

This study was undertaken in order to determine analytically the magnitude of the secondary (i.e., joint deflection induced) moments in the continuous glued-laminated chords of bowstring timber trusses. Traditionally, these moments have been assumed to be small and therefore neglected. The American Institute of Timber Construction makes no mention of these moments in their recommended design procedure.

A Study Of Single Angle Compression Members, James Robert Callaway

Dissertations and Theses

A study was undertaken to investigate the compressive capacity of a specific group of single angle members.

A review of existing literature and techniques was presented. Laboratory compression tests were performed on 22 angle members of four different sizes and two different lengths. Additional tests were performed to determine the yield strength of the material. The results, normalized with respect to the yield stress, were tabulated and discussed.

Two existing analytic models were used to attempt to predict the ultimate capacity of the test members. The first, an elastic method, was based upon the AISC combined stress equation. The second, …

Effects On Electrolytic Cells Of Magnetic Fields Applied To Single Electrodes, Craig Allen Cousins

Dissertations and Theses

The primary goal of this research was to investigate the effects associated with the application of magnetic fields to single electrodes.

Coherence Effects In Synchronously Pumped Mode‐Locked Dye Lasers, Lee W. Casperson

Electrical and Computer Engineering Faculty Publications and Presentations

A formalism is developed for describing the evolution of picosecond mode‐locked pulses in synchronously pumped dye lasers. The finite phase memory of the molecular wave functions is included, and it is found that the resultant coherence effects can be dominant for operation close to exact synchrony. Considerations of the isotropic molecular orientational distribution and the finite vibrational relaxation times are also essential in obtaining quantitative agreement with experimental results.

Thermal Hysteresis In Acoustic Resonators, Lee W. Casperson, Lloyd M. Davis, John D. Harvey

Electrical and Computer Engineering Faculty Publications and Presentations

In some applications of piezoelectrically driven acoustic resonators, the power dissipated in the resonating material may be sufficient to significantly change the temperature and hence the resonance frequency. A straightforward analysis shows that this effect can lead to severe hysteresis and thermal bistability. This model is in agreement with experiments that have been performed using a fused silica acousto‐optic modulator.

Investigation Of Blood Pressure Measurement Using A Hydraulic Occlusive Cuff, Kusha R. Bhattarai

Dissertations and Theses

This thesis presents an improved oscillotonometric system for the measurement of human blood pressure. The study included:

1. The design of a hydraulic occlusive cuff,

2. The investigation of the wave forms taken from the blood pressure measurements, and

3. The design of a mechanism for the simulation of human blood pressure pulse.

In this study, an experimental system consisting of a rigid shell occlusive cuff, a constant volume displacement pump, a transducer, and a chart recorder was designed and used for data collection.

Modes Of A Laser Resonator With A Retroreflecting Corner Cube Mirror, Guosheng Zhou, Anthony J. Alfrey, Lee W. Casperson

Electrical and Computer Engineering Faculty Publications and Presentations

The self-consistent integral equation for the field distribution of the resonant modes in a resonator with a tilted retroreflecting corner cube mirror is solved. The corner cube acts like a convex lens with radius of curvature -L cot²Ө in the rotation direction (L is the cavity length and Ө the rotation angle) and like a flat plane in the direction of the rotation axis. The field distribution can be described in terms of Hermite-Gaussian functions, and these results have been confirmed experimentally using an Ar-ion laser. The equivalent beam matrix for a reflecting corner cube is also found.

The Influence Of Halloysite Content On The Shear Strength Of Kaolinite, Reka Katalin Gabor

Dissertations and Theses

The objective of this thesis is to determine the relative shear strengths of halloysite, kaolinite, synthetic mixtures, and local soils, to investigate the influence of halloysite content on the shear strength of kaolinite, and to explore the possibility that the strength properties of soil clays might be controlled by the relative content of their component minerals.

Modes Of A Laser Resonator With A Retroreflecting Roof Mirror, Guosheng Zhou, Lee W. Casperson

Electrical and Computer Engineering Faculty Publications and Presentations

The self-consistent integral equation for the field distribution of the resonant modes in a resonator with a tilted retroreflecting roof mirror is solved. The field distribution in the direction of the roof can be described in terms of Hermite-Gaussian functions. The beam matrix for a retroreflecting roof is found, and a new type of resonator which does not need precise alignment is proposed.

Experimental Determination Of Post-Buckling Performance Of Steel Angles, Rupasiri Purasinghe

Dissertations and Theses

An experimental testing program was conducted to determine the compression member performance in post-buckling region. These results are compared with an analytical computer program developed by Portland State University under Bonneville Power Administration Contract 79-80BP 24005. The paper presents the sensitivity of the performance of single angle compression members to various parameters such as length to radius of gyration ratio, eccentricity, end conditions and yield stress. The effect of local buckling on long member performance is also documented.

Electromagnetic Modes Of An Inhomogeneous Sphere, Lee W. Casperson

Electrical and Computer Engineering Faculty Publications and Presentations

In many cases the electromagnetic modes of a sphere can be obtained exactly. Special simplifications occur when the conductivity, complex permittivity, and complex permeability vary only in the radial direction, and static and time dependent examples are discussed. With quadratic or Coulomblike permittivity variations, the wave functions resemble the quantum mechanical harmonic oscillator or hydrogen atom wave functions, and similar angular momentum operators are obtained.

Synthesis Of Gaussian Beam Optical Systems, Lee W. Casperson

Electrical and Computer Engineering Faculty Publications and Presentations

Systematic procedures are presented for determining the the optical components needed to obtain an arbitrary transformation of a propagating light ray or Gaussian beam.

Modes Of A Laser Resonator With A Retroreflective Mirror, Guosheng Zhou, Lee W. Casperson

Electrical and Computer Engineering Faculty Publications and Presentations

The self-consistent integral equation for the field distribution of the resonant modes in an inclined retroreflective grating resonator is solved in the limit of large Fresnel numbers. The transverse field distribution in the direction perpendicular to the grating grooves can be described in terms of Hermite-Gaussian functions provided that λ « d « w, where λ is the wavelength, d is the grating spacing, and w is the beam spot size.

Laser Broadening Ratio From The Multimode Oscillation Threshold, Lee W. Casperson

Electrical and Computer Engineering Faculty Publications and Presentations

Lasers with mixed line broadening typically oscillate in a single longitudinal mode for excitation levels only slightly above threshold. At high pump levels, less desirable multimode oscillation may sometimes occur. A procedure is described for using the multimode threshold as a sensitive measure of the broadening ratio, and GaAs is mentioned as an example.

Polarization Characteristics Of Dye‐Laser Amplifiers Ii. Isotropic Molecular Distributions, Lee W. Casperson, Kendall C. Reyzer

Electrical and Computer Engineering Faculty Publications and Presentations

In a previous study a general semiclassical formalism has been developed for lasers with arbitrary orientational distributions of the active molecules. Here that formalism is applied to the important case of an isotropic distribution of molecules, and this limit is especially relevant to liquid dye lasers. Extensive analytical and numerical results are presented for the polarization properties of such dye lasers. It is found that in general the polarization states of the pump and signal fields are coupled together and both change with distance in a laser amplifier.

Polarization Characteristics Of Dye‐Laser Amplifiers I. Unidirectional Molecular Distributions, Lee W. Casperson, Kendall C. Reyzer

Electrical and Computer Engineering Faculty Publications and Presentations

Many practical laser amplifiers exhibit anisotropic gain due to polarization of the pumping fields or to a fixed preferential alignment of the active dipoles. Several specific causes and consequences of gain anisotropy are discussed in detail. In the analysis, the emphasis is placed on dye‐laser systems including arbitrary amplitudes, phases, and polarizations of the pump and signal fields. Analytical results are presented for a unidrectional molecular distribution, and it is found that the polarization states of the pump and signal fields change with distance in the amplifier.

The Effect Of Residual Stress Distribution On The Ultimate Strength Of Tubular Beam-Columns, Steven L. Barrett

Dissertations and Theses

Using data for the longitudinal residual stress distribution in welded steel tubes, curves describing these distributions are selected for study. Each of these curves are checked for static balance across the tube cross section. The curves that exhibit an imbalance are adjusted by a combination of a simplified model for each and the use of a computer program that is developed to calculate the resulting forces and moments on the cross section. The residual stress in the area of the tube wall opposite the longitudinal weld is found to be the most important in the adjustment to obtain exact equilibrium. …

Laser Power Calculations: Sources Of Error, Lee W. Casperson

Electrical and Computer Engineering Faculty Publications and Presentations

The physical phenomena that dominate the power characteristics of a laser depend on the detailed nature of the amplifying medium and the resonator structure. In predicting the power characteristics, numerous approximations are always required. The most important approximations are considered here in detail, and error estimates are presented so that a designer can select the appropriate model for a particular application. Emphasis is placed on analytic solutions and specific phenomena considered include longitudinal and transverse spatial hole burning, large single-pass gain, and mixed line broadening.

Non-Linear Behavior Of Unbraced Two-Bay Reinforced Concrete Frames, Mehdi Shadyab

Dissertations and Theses

In this investigation, the primary objective was to study the nonlinear behavior of unbraced two-bay concrete frames and to determine the extent to which ultimate load theory or limit design can be applied to these structures. The frame behavior was investigated analytically by two methods. In the first method the frame stability equation was derived assuming that members of the frame possess an elasto-plastic moment-curvature relationship. This stability analysis was also carried out by another model consisting of a column attached to a linear spring and carrying the total frame load. The second method was through a computer program which …

Reduction Of Capacitor Switching Transients By Controlled Closing, John Herman Brunke

Dissertations and Theses

This thesis presents the theory, analysis, testing and implementation of a scheme to reduce shunt compensation capacitor switching transients. The described method is switch the capacitors very near the instant when the bus voltage is at a power frequency zero. This was accomplished with a vacuum breaker on a 230 kV shunt capacitor bank.

Computer Aided Optimal Design Of Helical Gears, S. N. Muthukrishnan

Dissertations and Theses

A random search method for optimum design of a pair of helical gears has been developed. The sequence of optimization consists of two principal components. The first is the selection phase, where the output is the starting solution for the design variables - module, facewidth, helix angle and number of teeth on the pinion. The input for the selection phase includes the application environment, approximate center distance, minimum helix angle, desired values of gear ratio, pinion speed and the power to be transmitted. The limits on each of the design variables and the constraints are imposed interactively during the first …

Properties Of A Coaxial Cw Co₂ Laser, T.-K. Cheng Ken, Lee W. Casperson

Electrical and Computer Engineering Faculty Publications and Presentations

A cw CO₂ laser has been developed in which the active medium is formed by a discharge between coaxial electrodes. The laser gain and saturation properties have been studied as functions of the various device parameters. Over-all efficiency is about the same as for a conventional longitudinal discharge laser, and advantages of the coaxial geometry include low voltage operation, rapid cooling, and rugged construction.

A Feasibility Analysis Of A Directly Sun-Pumped Carbon Dioxide Laser In Space, Seiichi Morimoto

Dissertations and Theses

The possibility of using sunlight to pump a CW carbon dioxide laser has been analyzed. Such a laser could be of interest for such applications as space communication and power transmission. In order to optically pump CO₂ using sunlight, the intense vibrational-rotational absorption bands of CO₂ in the 4.3 micron spectral region would have to be utilized. The total pumping power from sunlight can be calculated from the known data of the solar spectral irradiance outside the atmosphere and the infrared absorption by carbon dioxide at 4.3 microns. The pumping power is proportional to the collector area of …

Scalar‐Wave Approach For Single‐Mode Inhomogeneous Fiber Problems, Lee W. Casperson, Cavour W. Yeh, W. P. Brown

Electrical and Computer Engineering Faculty Publications and Presentations

It has generally been accepted that accurate results may be obtained using the scalar‐wave approach to solve problems dealing with inhomogeneous multimode guided‐wave structures. The problem of the applicability of the scalar‐wave approach to obtain wave propagation characteristics in single‐mode fiber or integrated optical circuit guides with inhomogeneous index profiles is examined in this paper. It is shown that if certain limiting conditions are satisfied, the scalar‐wave approach will yield valid results for single‐mode structures. These limiting conditions are usually satisfied by many practical single‐mode inhomogeneous fibers or IOC structures.

The Design And Construction Of A Flashlamp-Pumped Frequency-Doubled Dye Laser Applicable To Long Path Monitoring Of Air Pollutants, Joel Craig Johnson

Dissertations and Theses

The subject of this thesis is the development of a laser light source which could be used in an air pollution monitor to measure the average concentration of sulfur dioxide gas over long paths (>1 km). Many of the problems encountered in designing a long-path pollutant monitor such as instrument cost and reliability, the selection of an optimum spectral region for making the measurement, and light losses due to scattering and turbulence, are considered. The result of these considerations together with a survey of available laser light sources suggested that a frequency-doubled dye laser possessed several advantages over other …

Beam Deflection In A Pulsed Chemical Laser Amplifier, J. Munch, Lee W. Casperson, E. C. Rea

Electrical and Computer Engineering Faculty Publications and Presentations

Analyses and experiments have been performed to investigate deflection of a Gaussian beam propagating through an amplifying medium possessing a strong transverse gain gradient. The analysis includes effects due to dispersion and gain steering. The experiments were performed in a high power pulsed chemical laser amplifier using a cw frequency stabilized laser as a source. Time dependent beam deflection due to the interaction of the gain gradient with the finite radius of curvature of the propagating beam was observed.

Scattering Of Focused Beams By Tenuous Particles, S. Colak, Cavour W. Yeh, Lee W. Casperson

Electrical and Computer Engineering Faculty Publications and Presentations

This paper deals with the problem of the scattering of focused laser beams by tenuous particles using an iterative technique. The results are shown to be accurate provided that (a) the polarizability of the particle medium is small and (b) the phase shift of the central ray is less than 2. It was found that when the size of the incident beam waist is close to that of the scatterer, the scattered field deviates significantly from that for the incident plane wave case. Specific examples are given.