Laboratory and field studies of the fall armyworm, <i>Spodoptera frugiperda</i>, were undertaken to determine if a high larval rearing density produces premigrant traits, and if these traits can be used as criteria for separating nonpremigrant from premigrant groups. An increase in larval rearing density significantly decreased pupal weight and forewing width in the laboratory but not in the field. The greatest differences in developmental time among laboratory density treatments were 0.6 d and 1.07 d for females and males, respectively, but differences were not considered biologically significant. Rearing density did not affect duration of pupal stage in the field-reared fall armyworms. An actograph was used to measure adult flight activity and was validated with videotape recordings of moths in actograph cages. Behaviors other than flying occurred; hence, computer-recorded counts were termed activity counts (one activity count was recorded each time a moth broke an infrared beam directed through a window in an actograph cage). Male moths showed a greater proportion of long-duration activity bouts (spells of activity), a significantly greater activity bout duration, and a generally greater magnitude of activity during peak periods than female moths. Generally, actograph activity was not significantly affected by rearing density. Both mated and unmated females exposed to males showed very little actograph activity, and most of the females mated when exposed to males, regardless of rearing density. An increase in rearing density in the laboratory significantly increased adult lipid reserves, but higher lipid reserves were not related to a higher activity potential. Although larval rearing density did not affect wing-loading values, the fall armyworm as a migrant species showed lower than theoretically expected wing-loading values. Because some premigrant traits were produced by increasing the rearing density and other premigrant traits and behaviors were not produced, it is inconclusive that premigrants were produced by these rearing methods. Based on these results and data taken from the literature, there is reason to believe that the fall armyworm does not have a separable premigrant phase, and that components of weather are more influential than larval density in initiating its migratory behavior. / Ph. D.

Ferroelectric lead zirconate titanate thin films, Pb(ZrxTi 1-x)0 3 or PZT, have aroused considerable interest in recent years for the application in nonvolatile electronic memories because of their excellent ferroelectric properties. In this research, PZT thin films were studied from two aspects: the scientific aspect and the technical aspect. The optical properties of PZT solid solutions and the structure development in PZT films were extensively investigated in the scientific aspect. The PZT films used in this part of study were prepared by metalorganic decomposition (MOD) process. The envelope method, with consideration of light intensity loss from the back surface of the substrate, was demonstrated to be a simple and convenient tool for obtaining the optical properties of the PZT films in the medium and weak absorption regions. In the near optical band gap region, both the transmission and reflection spectra were used to successfully calculate the optical constants of the films. The film thickness derived from the envelope method was cross checked by a computer simulation method and was found to have an accuracy better than 2%. An effective, versatile, and nondestructive optical method was developed for the study of the structure development in MOD PZT films. Also, the models for the structure development were proposed and were verified by this optical method. Using this method, the characteristic temperatures (i.e., the initiation and completion temperatures) of each phase can be easily identified. In addition, the volume fraction of the perovskite phase in the pyrochlore-perovskite phase transformation region was obtained from this optical method. From the technical point of view, ferroelectric PZT films were successfully and reproducibly deposited for the first time by hot-wall metalorganic chemical vapor deposition (MOCVD). One of the problems associated with the MOCVD technique is the availability of the precursors. After intensive studies searching for the most suitable precursors for MOCVD PZT thin films, the safe and stable precursors, namely lead tetramethylheptadione [Pb(thd)2)], zirconium tetramethylheptadione [Zr(thd)4], and titanium ethoxide [Ti(OEt)4] were chosen. The films were deposited at temperatures as low as 55QOC and had pure perovskite phase in the as-deposited state. Also, the films were smooth, specular, crack-free, uniform, and adhered well on the substrates. The stoichiometry of the films can be easily controlled either by varying the individual precursor temperature and/or the flow rate of the carrier gas. Auger electron spectroscopic (AES) depth profile showed good uniformity through the thickness of the films. The AES spectra also showed no carbon contamination in the bulk of the films. As-deposited films were dense and showed uniform and fine grains. The film (Pb/Zr/Ti = 50/41/9) annealed at 6QQOC showed a spontaneous polarization of23.3 pC/cm² and a coercive field of 64.5 kV /em. / Ph. D.

La préparation pour la retraite à la période de la préretraite est mal documentée. Cette étude vise à connaître les déterminants des comportements préparatoires de la retraite. Un intérêt particulier est porté sur l'effet du genre, du statut professionnel, et des attitudes face à la retraite. Les sujets, au nombre de 119 (59 hommes, 60 femmes), sont âgés entre 40 à 64 ans ( X =50,83) et travaillent tous à temps plein. Les participants doivent répondre à un questionnaire par la poste, qui est composé d'une fiche signalétique, de l'Échelle Différentielle Sémantique (Atchley, 1974) et du Questionnaire de Préparation pour la Retraite. Des analyses de régression démontrent que le genre, le statut professionnel et les attitudes face à la retraite ne se présentent pas comme de bons prédicteurs des comportements préparatoires. Finalement, les cours de préparation pour la retraite, la satisfaction au travail, ainsi que la proximité exercent une influence favorable sur les activités préparatoires de la retraite.

One of the most controversial questions in public administration today is the question of effectiveness and how well it is achieved by public and private organizations. Some studies hold private enterprise up as more effective; however, some others have argued the case in favor of the public sector. In examining the question, theorists have largely neglected the issue of quality of service. This study generates an effectiveness rating that takes into account quality as a major factor in addition to costs. This research uses the largest manpower training program in America, Job Corps, as a model for study. Job Corps encompasses both the public and private sectors, with a majority of the 107 Job Corps centers managed by private enterprise under contract to the United States Government. Two public and two private Job Corps centers were compared. Data were compiled from the following sources: 1) direct personal observation; 2) in-depth interviews; 3) Job Corps financial reports; and 4) student survey results. An effectiveness quotient for each center was developed from the data. Results show that each of the four centers has its own characteristic strengths and weaknesses. The public centers offered somewhat better quality of services as well as lower costs, and therefore noticeably better effectiveness than did the private centers. The public centers also surpassed the private centers in successfully meeting the job satisfaction needs of their employees. Unexpected findings included the fact that the centers that kept their costs the lowest also had the highest quality, and thus were scored as more effective. We conclude that the differentiating factor between public and private Job Corps centers is not their ownership, public or private, but rather how well-managed a center or class of centers is. In order to improve Job Corps operations, this study recommends a change in the assessment procedures for Job Corps, emphasizing quality of services and effectiveness of services rather than statistics on cost and average length of stay. It also suggests that continuing attention be paid to program management systems, including elements as diverse as communication among staff and control of students. / Ph. D.

The main theme of this thesis is the formulation of self-duality for extended objects (p-branes). An approach to self-duality for membranes is developed using the correspondence between the large N limit of SU(N) gauge theories and the membrane theory. This correspondence is established via the use of the coadjoint orbit method. It is shown that classical gauge field theories can be formulated on the coadjoint orbits of an infinite dimensional group (a semidirect product of the group of gauge transformations and the Heisenberg-Weyl group); in Chap. II this construction is carried out for Yang-Mills, Cherns-Simons, topological Yang-Mills and F A B theories, as well as the Wess-Zumino-Novikov-Witten model. In Chap. III it is shown that for homogeneous fields (i.e. gauge mechanics) and in the N -1-" limit, the coadjoint orbit action becomes identical to the membrane action in the light cone gauge. The self-duality equations for gauge fields then translate into the self-duality equations for membranes. In Chap. IV another approach is developed, one which allows us to formulate the self-duality equations for a much larger class of extended objects. This generalized self-duality is based on the notion of p-fold vector products. We exhibit several classes of solutions for these generalized self-dual extended objects and classify all the cases in which they exist. We also show that the self-intersecting string instantons, introduced by Polyakov constitute a special case of these solutions. Of particular interest are two octonionic classes: a membrane in 7 dimensions and a 3-brane in 8 dimensions. To simplify the calculations in these cases we developed an approach to octonionic symbolic computing making use of "Mathematica". Some possible applications of self-dual extended objects are briefly discussed. / Ph. D.

The effectiveness of seven methods of handling missing data was investigated in a factorial design using random samples selected from the National Education Longitudinal Study of 1988 (NELS-88). Methods evaluated were listwise deletion, pairwise deletion, mean substitution, Buck's procedure, mean regression, one iteration regression, and iterative regression. Factors controlled were number of variables (4 and 8), average intercorrelation (0.2 and 0.4), sample size (200 and 2000), and proportion of incomplete cases (10%, 20%, and 40%). The pattern of missing values was determined by the pattern existing in the variables selected from NELS-88 data base. Covariance matrices resulting from the use of each missing data method were compared to the 'true' covariance matrix using multi-sample analysis in LISREL 7. Variable means were compared to the 'true' means using the MANOVA procedure in SPSS/PC+. Statistically significant differences (p≤.05) were detected in both comparisons. The most surprising result of this study was the effectiveness (p>.05) of pairwise deletion whenever the sample size was large thus supporting the contention that the error term disappears as sample size approaches infinity (Glasser, 1964). Listwise deletion was also effective (p>.05) whenever there were four variables or the sample size was small. Almost as surprising was the relative ineffectiveness (p<.05) of the regression methods. This is explained by the difference in proportion of incomplete cases versus the proportion of missing values, and by the distribution of the missing values within the incomplete cases. / Ph. D.

The first part of this research constituted the study of oligomeric incorporation into an inorganic network leading to the fonnation of a hybrid material by the sol-gel process. The oligomeric species chosen was silanol terminated poly(dimethylsiloxane) (PDMS) and the inorganic oxide precursor chosen was titanium tetra-isopropoxide (TIP). The rationale for choosing these materials stemmed from the desire to make materials for optical filters since a gradient of optical properties can be derived based on the composition and the initial reaction conditions. 29Si NMR studies were conducted to investigate the incorporation process which led to the conclusion that the PDMS chains were being degraded by the TIP. This problem led to the synthesis of TIP endcapped PDMS which was then used as the oligomeric component in the hybrid materials. The endcapping changed the functionality of the oligomer to six, and more importantly, its reactivity which was now closer to that of the TIP. Also, having the same functionality at the ends as the precursor affects the compatibility of the two components. Hybrid materials in the form of free standing films were fabricated from varying TIP/pDMS compositions and different initial reaction conditions. The hybrid materials synthesized were then subjected to a systematic structure-property relationship study. The degree of phase mixing or the encapsulation of the siloxane phase by the inorganic oxide increases with higher TIP content. This behaviour was seen by both the dielectric and dynamic mechanical studies. The modulus and the stress to break increased with higher TIP content while the strain to break decreased. At the 50/50 TIP/PDMS composition there was an abrupt change in the mechanical properties which signified a morphological change in these materials. The refractive indices of the materials also showed a trend similar to that of the mechanical properties. Three different cure procedures, viz., room temperature, thermal cure at 70 °C and microwave cure at 70 °C were utilized to fabricate the films. More phase separation occurred in the microwave cured over the thermally cured materials as evident from dielectric and dynamic mechanical studies. However, the effect diminished with higher TIP content in the materials. Changing the initial reaction conditions by varying the initial water and acid content changed the properties observed in the final products. Dielectric and dynamic mechanical studies showed that the phase separation was higher with increased water content. Also, the modulus of the materials made with increased water content was higher. Decreased acid content led to better dispersion of the two components as shown by the dielectric and dynamic mechanical experiments. The effect of using a less reactive inorganic component tetra-ethyl orthosilicate (TEOS), instead of TIP was also studied. The TEOS/pDMS materials showed more phase mixing than the TIPIPDMS materials, although, the dielectric tan δ peak maxima appeared at a lower temperature. The TEOS/PDMS materials were also less stiff than the TIP/PDMS materials. Structural studies were conducted by means of solid-state NMR, electron microscopy and small angle x-ray scattering (SAXS). With few exceptions, these studies correlated very well with the properties observed in these materials. The spin-lattice relaxation times obtained from the solid-state NMR correlated with the better phase mixing observed in the TEOSIPDMS materials relative to the TIPIPDMS materials. Electron microscopy in the backscattered mode showed the presence of microphase separation in these materials. At the 50/50 TIPIPDMS composition connectivity of the inorganic oxide phase was complete, perhaps encapsulating the siloxane phase totally. Microstructural differences were observed due to the variation in the cure modes. The domain sizes of the oxide phase were finer in the thermally cured as compared to the room temperature cured materials. Higher water content led to a very different microstructure when compared to materials made with lower water content. Smaller spherical particulate type structures were observed in the material made with higher water content. The domain sizes of the oxide phase in the TEOS/PDMS material were bigger than those in the TIP/PDMS material of equivalent composition. These differences may be intimately related to the reactivity difference between TIP and TEOS. The SAXS data supported the microstructure seen by electron microscopy and the properties observed by dynamic mechanical, dielectric and mechanical studies. / Ph. D.

The research contributes toward a fully integrated multidisciplinary wing design synthesis by development of an appropriate structural model. The goal is to bridge the gap between highly idealized structural beam / aerodynamic strip models and the very detailed finite element and computational fluid dynamics, FEM/CFD, techniques. The former provides insufficient accuracy for flutter analysis of modern low aspect ratio composite wings. The latter is too computationally intensive for use in the inner loop of a simultaneous multidisciplinary optimization problem. The derived model provides a useful preliminary design tool as well. / Ph. D.

Low temperature phase relations in the ice-stable field of the system NaCl-CaCl₂-H₂O were determined under 1 atm. total pressure along the NaCl-H₂O and CaCl₂-H₂O binaries and along five pseudobinaries with constant NaCl/(NaCl+CaCl₂) weight ratios. The results are in excellent agreement with published data along the NaCl-H₂O binary but show large discrepancies when compared to previous determinations of the ice liquidus along the CaCl₂-H₂O binary and in the NaCl-CaCl₂-H₂O ternary. At moderate to high salinities, isotherms cross the ice sub-field at lower total salt concentrations than previously reported. In addition, NaCl/(NaCl+CaCl₂) weight ratios estimated from hydrohalite- and ice-melting temperatures may be low by as much as 15%. Relative densities were measured for NaCl(aq) and CaCl₂(aq) solutions to 250°C and 400 bars and over the range of ionic strengths 0.2 - 5.5 and 0.2 - 19.2 mol·kg⁻¹, respectively. The results span the pressure and temperature of earlier volumetric studies and extend to higher molalities than reported previously. The relative densities have been fitted as apparent molar volumes (V_Φ) using the Pitzer ion-interaction treatment, with appropriate expressions chosen for the temperature- and pressure-dependence of the virial coefficients of the model. The results presented for NaCl(aq) are in good agreement with published results to 250°C. The results presented for CaCl₂(aq) are in good agreement with published values to approximately 125°C. Above 125°C the inter- and intralaboratory precision of the published data deteriorate and are often in very poor agreement with the data from this Study. The representation for V_Φ for CaCl₂(aq) was integrated with respect to pressure to establish the pressure dependence of excess free energies over the temperature range studied. CaCl₂ activity coefficients (γ±) have been derived to 250°C, 400 bars and 4 mol·kg⁻¹ using published fits of CaCl₂ activity coefficient data along the vapor saturation surface and the pressure dependence determined in this work. The volumetric data indicate that the mean ionic activity coefficient, γ±(CaCl₂), increases by a maximum of 32% at 400 bars, 250°C, and 4 mol·kg⁻¹ as compared with its value at saturation pressure. Relative densities were also measured for several ternary { NaCl+CaCl₂}(aq) solutions at 25 and 35°C and 1 atm. These results substantially expand the volumetric data base for ternary solutions. Based on the results of this study most of the previously reported 308.15 K density data in the ternary appear to contain large errors. / Ph. D.

Research and Development (R&D) project selection has been the focus of much research attention and the literature on this subject is extensive. Numerous models have been proposed to facilitate the selection of R&D projects, and these models have been both qualitative and quantitative in nature. Various project goals are typically included in the selection process. For goals that can be developed as mathematical functions, models have been developed that determine optimal solutions efficiently. However, when project goals cannot be structured as linear or nonlinear functions, or to do so would make the solution of the model complex or even impossible, the models presented in the literature either make simplifying assumptions about these goals, or do not include them in the model. One goal that cannot be structured in an optimization format, is scheduling of projects through the R&D process. The nature of scheduling is such that it is difficult to include in any of the existing quantitative selection models, and the result is that scheduling goals are either considered after the projects have been selected, or they are not included at all. In this research an R&D selection model is developed that incorporates the scheduling of individual projects as one of several goals. The model is designed to reflect a realistic R&D situation, in terms of problem size, goals, objectives, and, constraints. In order to incorporate a scheduling goal, the model uses a heuristic approach to determine a solution. The validity of the solutions, as well as the computational complexity of the model are explored. / Ph. D.