Design characteristics and some applications of the ruby laser

This thesis is concerned with the solid state ruby laser, and the determination of the optimum design parameters upon which its performance is dependent. The voltage, current and light output characteristics of the linear xenon flashtuhes used for excitation are measured for different discharge circuit conditions, and the efficiency of laser operation is related to these different operating conditions. It is shown that two factors affect the coupling efficiency of the cylindrical ellipse which is used to transfer the radiation emitted by flashtube to the ruby rod: its geometric shape and the reflectivity of its walls. The theory describing the coupling efficiency of the single elliptical cavity is extended for the case of multiple section elliptical cavities, and experimental measurements of laser output energy and efficiency are made for both single and double cavities which are found to agree with theoretical predictions. A theory relating the optimum laser mirror reflectivity to the ruby dimensions and pump energy is developed, for which laser output energy measurements made with ruby rods from 2" to 6(^1)(_2) in length are found to be in agreement. This work also enables the total internal loss of each ruby to be determined and thus gives a method of assessing their quality. It is also demonstrated that the laser efficiency is strongly dependent upon the ruby temperature and the laser output energy is measured at temperatures of up to 50ºC above ambient conditions. The last chapter is concerned with a theoretical and practical assessment of the application of the ruby laser for machining and welding

Mechanization of and experience with a triplex fly-by-wire backup control system

A redundant three-axis analog control system was designed and developed to back up a digital fly-by-wire control system for an F-8C airplane. Forty-two flights, involving 58 hours of flight time, were flown by six pilots. The mechanization and operational experience with the backup control system, the problems involved in synchronizing it with the primary system, and the reliability of the system are discussed. The backup control system was dissimilar to the primary system, and it provided satisfactory handling through the flight envelope evaluated. Limited flight tests of a variety of control tasks showed that control was also satisfactory when the backup control system was controlled by a minimum-displacement (force) side stick. The operational reliability of the F-8 digital fly-by-wire control system was satisfactory, with no unintentional downmodes to the backup control system in flight. The ground and flight reliability of the system's components is discussed

Comet nongravitational forces and meteoritic impacts

We have considered those comets whose original orbits have been determined to be hyperbolic when only planetary perturbations are accounted for. It is found that formally unbound incident trajectories correlate most confidently with orbits that have small perihelion distances and move in a retrograde sense relative to planetary motion. Arguments are presented that these results are not due to measurement error or to selection effects. We conclude that the phenomenon is attributable to enhanced volatility leading to abnormally large nongravitational forces. Since the effect is absent in the prograde small-perihelia population, increased insolation is not the sole explanation. It is suggested that the significance of the retrograde correlation is connected with a larger energy of relative motion between retrograde comets and a population of prograde ecliptic meteoroids which impact the comet mantle exposing the underlying volatiles. The subsequent enhanced outgassing is the cause of the larger nongravitational forces

Mechanization of and experience with a triplex fly-by-wire backup control system

A redundant three axis analog control system was designed and developed to back up a digital fly by wire control system for an F-8C airplane. The mechanization and operational experience with the backup control system, the problems involved in synchronizing it with the primary system, and the reliability of the system are discussed. The backup control system was dissimilar to the primary system, and it provided satisfactory handling through the flight envelope evaluated. Limited flight tests of a variety of control tasks showed that control was also satisfactory when the backup control system was controlled by a minimum displacement (force) side stick. The operational reliability of the F-8 digital fly by wire control system was satisfactory, with no unintentional downmodes to the backup control system in flight. The ground and flight reliability of the system's components is discussed

Optical Astronomy from Orbiting Observatories

Atmospheric extinction, seeing, and light pollution £re the most significant factors affecting the quality of observations obtained from ground-based optical telescopes, degrading resolution and limiting reach. In addition, the earth\u27s atmosphere is opaque to radiation shorter than 0.3 microns preventing the ultraviolet from being observed in detail from the ground. The solution to these problems has been to move astronomical telescopes into earth orbit. Initially these orbiting observatories carried instruments sensitive to ultraviolet and higher energy radiation since it was otherwise unobservable. The success of the first series of these orbiting observatories, the Orbiting Astronomical Observatories (OAO), established these satellites as one of a new generation of tools for exploring the universe. Another orbiting observatory, the International Ultraviolet Explorer (IUE), is unique among the current orbiting observatories in that it is in a geosynchronous orbit and provides a guest observer facility serving the international community. IUE has had a significant impact on observational astronomy. Nearly 10 percent of all observational papers published JLi the Astrophysical Journal in 1980 reported or used observations made by IUE. The figure for all astronomical satellites is about 3 times higher and continues to rise. With the orbiting of the Space Telescope in the mid 1980s by the Space Shuttle, observational astronomy will enter a new era. For the first time, astronomers will have access to a large (2.4 meter) high-resolution telescope unhindered by the earth f s atmosphere. With the potential such an instrument offers, there is little doubt that the near future will see a large fraction of observational astronomy performed from orbiting observatories

Failures of Quay Walls During Chilean Earthquake of March 1985

Extensive damage took place in the quay walls in the Ports of Valparaíso and San Antonio during the Chilean earthquake of March 1985. Different types of retaining structures such as gravity retaining walls built with concrete blocks, sheetpiles and decks on vertical piles were subjected to large shaking ranging from 0.3 - 0.45g at Valparaíso Port to more than 0.6g at San Antonio. Some of the retaining structures collapsed and others behave quite well. In addition, some liquefaction and settlements in the sandy fill below the yards did occur at San Antonio, along with permanent displacements in the fill slope behind some of the decks supported by piles. The behavior of 7 berths at Valparaíso and 7 berths at San Antonio is discussed taking into account soil characteristics and field measurements performed after the earthquake

Tryptophane Metabolism X. The Effect Of Feeding 1(-)-, Dl-, And D(+)-Tryptophane, D(-)And Dl-(β-3-Indolelactic Acid,(β-3-Indolepyruvic Acid, And L(-)Kynurenine Upon The Storage Of Liver Glycogen And The Urinary Output Of Kynurenic Acid, Kynurenine, And Total Acetone Bodies

The amount of tryptophane required for maintenance and growth is small (2). When an excess is supplied to some animals, kynurenic acid is excreted (3) and, under certain conditions, kynurenine also (4). Although these are quantitatively the most important of the known metabolic products of tryptophane, the amounts excreted in extensive tests in the dog and rabbit have usually accounted for less than half, more often for less than a third, of the tryptophane administered (4-6)

Tryptophane Metabolism X. The Effect Of Feeding 1(-)-, Dl-, And D(+)-Tryptophane, D(-)And Dl-(β-3-Indolelactic Acid,(β-3-Indolepyruvic Acid, And L(-)Kynurenine Upon The Storage Of Liver Glycogen And The Urinary Output Of Kynurenic Acid, Kynurenine, And Total Acetone Bodies

The amount of tryptophane required for maintenance and growth is small (2). When an excess is supplied to some animals, kynurenic acid is excreted (3) and, under certain conditions, kynurenine also (4). Although these are quantitatively the most important of the known metabolic products of tryptophane, the amounts excreted in extensive tests in the dog and rabbit have usually accounted for less than half, more often for less than a third, of the tryptophane administered (4-6)

Initial Results from a Stacked Ring Apparatus for Simulation of a Soil Profile

A stack of 48 rings, lined with a latex membrane, is used to confine a column of soil 12 inches high by 12 inches in diameter (300 mm x 300 mm). Both dry and saturated columns of fine sand are shaken at their base, at a centrifugal acceleration of 35.5 g. Measurements of the settlement of the surface, horizontal displacement and pore pressures show that the columns of soil are behaving essentially (although not exactly) as one-dimensional shear beams

The Quest for Ground Truth in Musical Artist Similarity

Describes work by the Laboratory for Recognition and Organization of Speech and Audio, Department of Electrical Engineering, Columbia University, on attempting to define a single matrix of similarities between 400 different pop music artists, including survey website (musicseer.com) which attracted over 20,000 similarity judgments