The treatment of gamma-Fe₂O₃ with cobalt(II) is an important commercial process since the product is used extensively as a magnetic material for magnetic recording. The preparation of cobalt-doped gamma-Fe₂O₃ consists of interacting Co(II) with particulate gamma-Fe₂O₃ in solution under alkaline conditions. The surface of cobalt-treated gamma-Fe₂O₃ was characterized using the surface analysis techniques of x-ray photoelectron spectroscopy (XPS) and secondary ion mass spectroscopy (SIMS). Characterization was also accomplished using infrared spectroscopy and quantitative analysis. Surface analysis results suggest that the Co(II) is initially adsorbed as a hydrous precipitate during base addition (NaOH or NH₄OH). Following base addition, the reaction suspension was heated to 90-95°C. Results from surface analysis indicate that during this warm up period there is a conversion from the hydrous surface to a surface with a composition near CoFe₂O₄ (cobalt ferrite). No oxidation of Co(II) to Co(III) was observed. Surface analysis also suggests that cobalt-treated γ-Fe₂O₃ prepared using NaOH has a different surface chemistry than cobalt-treated γ-Fe₂O₃ prepared with NH₄OH. Following the adsorption of Co(II) on γ-Fe₂O₃ the product underwent a thermal treatment to enhance the coercivity. Surface analysis results indicate that the thermal treatment causes a significant diffusion of Co(II) into the bulk γ-Fe₂O₃. The results also suggest that the coercivity enhancement following thermal treatment is largely due to the inward diffusion of Co(II) and not a change in the surface composition of the cobalt-treated γ-Fe₂O₃. / Master of Science

A rapidly scanning directionally-sensitive three-velocity - component laser Doppler anemometer has been developed. It permits scans through 3-dimensional flows to obtain space-time velocity information. Since it has lower signal-averaging bias than pointwise measurements, only short record times are required to obtain sufficient data for statistical averages and, hence, it enables rapid mapping of the U, V, and W velocities in such flows. A flexible optical system allows for easy variation of the fringe spacings as well as the location and the size of the measurement volume. The optical paths are equalized without use of any additional optical components. A Ronchi Ruling is employed to create a horizontal stationary fringe pattern, and a dual Bragg cell is used to produce sets of moving vertical fringes. It is also shown that a scheme proposed by other workers, relying on a fringe pattern moving in the on-axis direction, will not work. The Doppler frequency is independent of the position of the receiving optics, and only one photomultiplier tube is needed to receive the signals for all three velocity components. Measurements made on a stationary solid object as well as in a dispersion of particles in water show that signals with low noise level and high fringe visibility are obtained. / M.S.

This study investigated the relative effectiveness of two group approaches to weight control, one which used a standardized diet with recipes (Redbook Wise Woman's Diet) and the other with an individualized exchange diet and one individual dietary counseling session with the investigator. Except for the dietary component, the two groups had eight identical weekly program outlines. Both groups were compared to a control group receiving standard out-patient treatment approach of one individualized dietary counseling session followed by weekly weigh-ins. There was no significant difference between treatment groups using either change in body weight or change in triceps skinfold measurements as the variable, at either the end of the treatment or at follow-up. This study also looked at eight of the Adjective Check List (ACL) Scales (defensiveness, self-confidence, personal adjustment, interception, heterosexuality, change, abasement and counseling readiness) as a means of predicting successful weight loss (more than five pounds) and the likelihood of completing the program. Participants who lost more than five pounds scored significantly lower on the change scale (p< .05) of their initial ACL questionnaire. Participants who dropped out of treatment scored significantly higher on the self-confidence (p<.05) and counseling readiness (p<.05) scales. Finally, this study evaluated changes in dietary intake before and after treatment. At the end of treatment, dietary intake of total kilocalories and percent of calories consumed as fat both significantly decreased, while the percentage of calories consumed as protein increased significantly. / M.S.

This study investigated the potential use of wide skidder tires for forest harvesting operations on steep slopes. During the summer of 1984, field tests were conducted to compare the performance characteristics of 24.5-32 and 66-43 rubber tires on a JD-640 grapple skidder loaded with tree length material. The skidder was operated on 20%, 25% and 30% slopes on Piedmont soils near Rome, Georgia. Video recorders were used to document the field measurements and observations of machine travel time and wheel slip over defined courses. Soil compaction was evaluated by comparing soil cone penetrometer readings taken in the wheel tracks of the test lanes to those taken in undisturbed adjacent areas. Skidder lateral stability was analyzed using the mathematical model developed in this study. Based on the results of statistical analyses of the data and field observations obtained under the test conditions, the skidder equipped with wide tires generally attained higher average speeds, tended to cause less wheel slip, resulted in smaller increases in soil cone penetrometer readings, and had significantly greater stability on sideslopes than the skidder equipped with the narrow tires. The stability model developed in this study predicted the critical sideways tipping angle for a JDâ 64O grapple skidder to be approximately 32° when fitted with the 24.5-32 tires, and 44° when fitted with the 66-43 tires. / Master of Science

Soil water movement and desorption studies were conducted on two agriculturally important soil series. The soils selected were the Norfolk soil (a fine loamy, siliceous, thermic, Typic Paleudult) and the Cecil soil (a clayey, kaolinitic, thermic, Typic Hapludult). Water desorption properties were investigated in the laboratory and in situ. The soil water desorption curves developed in the laboratory for both soils were relatively uniform. This observation was also true for most horizons for the desorption curves developed from the field data. The results for the B horizons of the Cecil soil showed the greatest variability, with the field data being the most variable. Comparisons of the field and laboratory water contents at given tensions show the field values were lower than laboratory values for horizons with over 40 percent sand and less than 30 percent clay. Field values were higher than laboratory values in the B horizons of both soils. In all other horizons, the field values were close to those obtained in the laboratory. The Norfolk soil was found to contain more plant available water than the Cecil soil. The selection of an upper limit for plant available water estimation is critical, especially for the Norfolk soil. The Cecil soil yielded little water between -.05 and -.30 bars, whereas the Norfolk soil yielded a relatively large amount of water (more than 3 times greater) in this range. This would nearly double the predicted plant available water for the Norfolk soil. Results of this study show that the irrigation management of the Cecil soil would require smaller amounts of water applied frequently, whereas the Norfolk soil could hold larger amounts of plant available water applied less frequently. This would allow more time between irrigations. / Master of Science

Master of Architecture

Distortions and changes in orientation of a 30° wye pile assembly were monitored in an attempt to improve our understanding of this critical connection in cellular cofferdams. Main cell, arc cell and common wall hoop tensions were simulated by applying axial loads to the three wye legs. Loads and displacements were monitored by a microcomputer aided data acquisition system. All of the behaviors studied exhibited some dependence on the ratio between the forces applied to the main and arc cell legs of the wye. Applied loads varied in magnitude and proportion, and the assembly re-oriented to new equilibrium positions. These positions were found to be predictable by solving three non-linear equilibrium equations of a statically determinate model. Common wall tension was observed to exceed main cell tension by 10-80% depending on the ratio of applied loads. Interlock load-deformation responses were measured for interlocks at which connecting piles were not coaxial. Wye angle deformations were found to be very small in the test loading range. The results of this investigation may be useful in developing parameters for and comparing results from finite element models of cellular cofferdams. / M.S.

« Dans le cadre de cette thèse de création, nous avons préjugé (et non méjugé, espérons-le) de nos dons drôlatiques et tenté d'appliquer dans des nouvelles de différentes longueurs les procédés que Bergson a dégagés d'oeuvres comiques. « Dan Druff », « Au-delà du bien et du mal » et « Le Bébé de Rosemarie» font appel aux procédés du comique de situation. « Sarah » utilise les procédés propres au comique de caractère. Enfin, « La mission de Jérome », « Un horla dans le frigo » et « Le Nauséeux » sont l'application des procédés du comique de mots. Dans la partie critique, nous exposerons dans ses grandes lignes la théorie d'Henri Bergson sur le comique, puis décrirons plus en détail les procédés employés dans nos nouvelles pour ensuite discuter des résultats de l'application. Au besoin, nous recourrons à d'autres théories explicatives du comique. »--Pages 4-5

The purpose of this study was to find the difference, if any, between the weight gain patterns during pregnancy of women attending public health clinics in Northern Virginia who were enrolled in the NIC program and women not enrolled in the NIC program. Women on the NIC program during pregnancy were identified from NIC files. The control group was chosen from among women who were shown to be both nutritionally at risk and eligible for NIC based on income, but who were not receiving NIC benefits during pregnancy. The sample consisted of M8 subjects in each group who met certain other selection criteria. With the exception of income, there was no statistically significant difference when selected maternal and infant variables were compared. There was no significant difference (p>.O5) between total weight gain of the two groups, although the NIC mothers gained slightly more during pregnancy than the non-NIC mothers. A series of t-tests, performed between the means of the weekly weight gains, showed no significant difference in the weekly weight gain of the two samples at any week of pregnancy. Both samples had increased weekly weight gains near the end of pregnancy - the mean of the non-WIC group was higher and occurred slightly later than did that of the WIC group. These higher means near the end of pregnancy for the non-WIC group resulted in statistically significant differences in the two groups when comparing the last part of pregnancy and suggest that the non-WIC group is gaining a larger amount of weight very late in pregnancy. / Master of Science

The use of wood stoves for residential heating has been increasing over the past several years. This increased use of wood stoves has caused significant concern about increased air pollution. Development of improved emissions and efficiency measurement methods will allow the development of improved stoves. Room calorimetry is used as the standard for measuring the energy efficiency of stoves. Unfortunately, this method is expensive and few wood stove manufacturers can afford it. For this reason, flue loss methods which are generally less expensive are attractive. Flue loss methods measure either directly or indirectly the following instantaneous losses: 1. Sensible energy loss due to the flue gases being at a higher temperature than the ambient. 2. Chemical energy loss from incomplete combustion. 3. Latent energy loss due to water existing as a vapor in the flue gas. This loss is included since the higher heating value of wood is used. The instantaneous efficiency of the stove can then be determined from measurement of these three losses and the instantaneous energy input. This project is part of a larger project which has an overall objective to develop an accurate flue loss method. An accurate flue loss method is needed since many of the traditional flue loss methods have unknown accuracies. / Master of Science