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Thesis (M.S.)--University of Wisconsin--Madison, 1971. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1957. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 305-310).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1968. / Typescript. Vita. Includes bibliographical references (leaves 100-104).

The purpose of this study was to investigate the effect of class size on student achievement in attaining two of the objectives of learning, namely, remembering and understanding, as these objectives are associated with the subject matter presented. To permit a statistical analysis of the data collected, the following hypotheses were proposed: 1. Class size will not be a significant factor in student achievement in remembering, by recognition or recall, discrete items of information. 2. Class size will not be a significant factor in student achievement in understanding the concepts and generalizations presented. Student achievement for each objective was defined as the difference between the scores obtained on alternate forms of the measuring instrument administered before and after the experimental period. The objectives of learning for this study, namely remembering and understanding, were limited to the equipping of each student with: 1. a specific body of information (Remembering), 2. the understandings necessary to make full use of the information learned (Understanding). The investigation was undertaken by teaching a chemistry unit to three matched classes of grade ten Science 20 students. The classes of fourteen, twenty-eight and fifty-six students respectively were matched for means and standard deviations on the basis, of the student's Otis I.Q. scores, previous science performance scores and chronological age and sex. The learning material taught during the investigation was based upon the topics covered by the Anderson Chemistry Test. Each of the classes was taught by the investigator, using the lecture-question-discussion method. Student achievement on the Anderson Test was measured by applying the "t" ratio test to the difference between the means of the classes, for each objective of learning. The difference between means was deemed significant if "t" reached the 0.01 level of confidence. Since "t" did not approach this level for any of the objectives tested it was concluded that, within the conditions imposed by this study, class size might possibly be as large as fifty-six without significantly changing student achievement. This conclusion is valid only within the limitations of this study, namely; 1. The population available. 2. The method of assigning students to classes. 3. The objectives of learning selected. 4. The way in which the objectives were defined. 5. The teaching method. 6. The number of teachers and classes involved. This study does not conclude that class size, alone, is an insignificant factor in student achievement. Rather, that class, size might be an insignificant factor for some objectives of learning when the traditional method of teaching is used. The scope of the investigation makes any definite conclusion questionable. / Education, Faculty of / Graduate

Thesis (Ph. D.)--University of Wisconsin--Madison, 1972. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

From a theoretical point of view, competition for the educational resources at the family and the population levels may change as the demographic transition advances. Although family size started to decline in the mid-1960s in México, the reduction in the size of the cohorts that compete for educational resources has recently occurred and it is an ongoing process in most municipalities of the country. Therefore, the main goal of this study was to examine the relationship between teenagers’ education and the demographic transition in México. The study explored if the teenagers’ school enrollment, age-grade delay at school and lower-secondary school attainment were linked to the teenagers’ number of siblings, as well as their cohort size in the municipality of residence in 2000. The 10% sample of the Mexican Housing and Population Census of 2000 was used as the main source of information. The study employed multivariate logistic regression models to accomplish its goals. Interactions between number of siblings and cohort size were tested. Also, interactions between these indicators and the teenagers’ gender and socioeconomic status were assessed respectively. The results indicated that contextual factors explained the initial negative association between teenagers’ education and cohort size, since this association disappeared or became small and positive after the addition of covariates. The Mexican educational system seems to have had the capacity of absorbing the demands in school coverage of the growing teenage population. The study revealed, however, that there was a large and negative association between teenagers’ education and number of siblings. Moreover, the study showed that the odds of the educational outcomes generally experienced larger changes by each additional sibling in the places where the demographic transition is more advanced, as well as among females and among the teenagers with high socioeconomic status. These results suggest that the educational disadvantages associated with multiple siblings may become more pronounced in the future and within certain contexts, as the demographic transition continues and big families become a smaller proportion of Mexican families. / text

Crystallite (or grain) size and strain within a polycrystalline material may have a profound influence on its physical properties, eg. the fracture toughness, wear and thermal shock resistance. A diffraction pattern for a material conveys information about the strain through the strain-induced changes in the shapes of the Bragg peaks and also through peak shifts. Crystallite size effects also influence the peak shape. Therefore, it is possible, in principle, to extract descriptions of crystallite size and strain from the peak broadening of a diffraction pattern. Various methods for size and strain evaluations have been proposed for extraction of the size and strain information in metals and ceramic powders. However, there appear to be no detailed amounts in the literature to be on the development of models appropriate for sintered ceramic materials. The objectives for this study were to critically examine the existing models for crystallite size and strain assessments and then to develop a new physically-based model which might be appropriate for sintered ceramics. The principal steps for the research, designed to fulfill the study objectives, were (1) acquiring high-quality diffraction data with synchrotron radiation, laboratory x-ray and neutron diffraction techniques for model evaluation; (2) performing preliminary evaluation using the existing models; (3) developing a new model and the non-linear least-squares calculation software; and (4) performing peak profile analyses using the existing and new models to evaluate the effectiveness of the new model. A convolution model for crystallite size and strain determination from diffraction line broadening has been developed with particular reference to the characterisation of sintered ceramics. / The size profile component function for the convolution model involves the modal size and the size distribution appropriate for `normal' crystallite growth according to the mean-field theory, as proposed recently in a seminal publication by Dr. Brian York of IBM. A Gaussian strain profile component function was considered in the study on the basis that it has been widely used for specimens which exhibit small microstrain (ca. 10-3 or less). The overall profile describing the diffraction pattern involves convolution of the instrument, size and strain effects. A non-linear least-squares refinement program entitled MOZAIX has been developed for profile fitting with the model. Data simulations were performed with the model, and non-linear least-squares optimisations for fitting the simulated data showed that the calculations were reasonable for low-strain sintered ceramics. The convolution model for size and strain assessments from diffraction line broadening has been evaluated with synchrotron and laboratory x-ray radiation diffraction data (SRD and XRD, respectively). The study made use of MgO ceramics with three different purity levels which had been sintered at a range of temperatures in order to provide diffraction data with a range of microstructural strain and size effects. The cubic symmetry of MgO provided isotropic size and strain effects as had been anticipated. The Voigt function, a convolution of the Gaussian and Lorentzian functions, is widely used to extract crystallite size and strain information from powder diffraction data using (1) Fourier transforms, (2) the Rietveld method and (3) integral breadth methods. Size and strain model evaluation carried out using the Voigt-based Rietveld and integral breadth methods assumes that the size effect contributes only to the Lorentzian component and the strain contributes only to the Gaussian component. / Size and strain assessment using the Voigt integral breadth single-line and Rietveld methods has been examined in this study with diffraction data for MgO ceramics. Two major outcomes from the evaluation confirmed impressions gained from the literature that: 1. the integral-breadth single-line method can be used as a reliable technique for size and strain analysis; 2. analysis using the Voigt function has no physical basis, is inappropriate for profiles with 'super-Lorentzian' character and is inadequate for size-strain analysis since the function does not take into account the size distribution parameter. There has been a strong trend recently towards whole-pattern size and strain evaluations which are progressively replacing single-line methods. However, due to time constraints, this study was confined to single-line analysis with the focus being on the development of the model, and with an expectation that the single-line model would readily be extended in the future to use with whole-powder pattern data. The size-strain analysis results using the convolution model showed that sintering (1) promotes crystallite growth and (2) relieves residual strains in low density sintered ceramics and introduces strains in dense ceramics, presumably due to grain-grain shear interactions. The effect of sintering on the size distribution clearly depends on the crystallite growth behaviour. Comparing the SRD convolution size results with those from scanning electron microscopy (SEM) showed that (1) the "grains" imaged using SEM contain clusters of crystallites and (2) the SEM-derived and convolution size distributions are in a satisfactory agreement. / In general, despite the larger uncertainties due to instrument resolution, the XRD results are in agreement with those from SRD. The size and strain values obtained with the convolution model were compared with those calculated using the Voigt single-line integral-breadth method. The comparison showed that size and strain results for both methods were dependent upon the character of the diffraction peak shapes. The convolution model improves the Voigt model in terms of (1) reliability of models from a physical point of view, (2) the additional size distribution parameter and (3) its applicability to `super-Lorentzian' profiles. Subsequent research is suggested to further improve the model in dealing with large microstrains and developing a whole powder fitting procedure.

An experimental investigation was performed to study the influence of the bubble size on an effervescent atomization. Experiments were conducted in horizontal facility with a 25.4mm diameter feeding pipe using water and air as the working fluids that were sprayed through an effervescent nozzle. Water flow rates from 113 to 189 kg/min and air to liquid mass ratios from 1% to 4% were selected. High speed photographs, of the bubbles in the feeding conduit and of the resulting droplets on the spray, were taken to use the particle projected areas to estimate their sizes. A monotonic positive correlation was found between the bubble size and the droplet size, in a fairly narrow range of feed flow void fractions. A bubble size sensitivity parameter was defined. Knowledge of the droplet behaviour provides data to enhance the design and operating conditions of the atomization process and a means to control droplet size.

An experimental investigation was performed to study the influence of the bubble size on an effervescent atomization. Experiments were conducted in horizontal facility with a 25.4mm diameter feeding pipe using water and air as the working fluids that were sprayed through an effervescent nozzle. Water flow rates from 113 to 189 kg/min and air to liquid mass ratios from 1% to 4% were selected. High speed photographs, of the bubbles in the feeding conduit and of the resulting droplets on the spray, were taken to use the particle projected areas to estimate their sizes. A monotonic positive correlation was found between the bubble size and the droplet size, in a fairly narrow range of feed flow void fractions. A bubble size sensitivity parameter was defined. Knowledge of the droplet behaviour provides data to enhance the design and operating conditions of the atomization process and a means to control droplet size.