Thesis. 1979. M.S.--Massachusetts Institute of Technology. Dept. of Aeronautics and Astronautics. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND AERONAUTICS. / Includes bibliographical references. / M.S.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / Nas ultimas dÃcadas, tÃm-se observado que a prÃtica da tatuagem adquiriu novas formas de usos e valores sociais, perdendo muito da sua aura de marginalidade, disseminando-se com poucas restriÃÃes de classe, gÃnero ou idade. Antes restrita a meios marginais, foi recentemente convertida em objeto de consumo, amplamente publicizada, alargando sua parcela de consumidores, exigindo novos procedimentos sanitÃrios e transformando o oficio de tatuador em uma ocupaÃÃo lucrativa. A partir da observaÃÃo de campo em trÃs estÃdios de tatuagem na cidade de Fortaleza, abordo o fenÃmeno focando nas trajetÃrias de seis tatuadores. Os procedimentos metodolÃgicos adotados foram entrevistas semi-dirigidas com os tatuadores, conversas informais com clientes e a observaÃÃo participante nos estÃdios. Os dados colhidos sugerem que os tatuadores, majoritariamente oriundos de classes populares, encontram na prÃtica da tatuagem um modo de ascender socialmente, evitando as profissÃes normalmente reservadas a indivÃduos de baixa escolaridade e oriundos de famÃlias humildes, surgindo como uma opÃÃo viÃvel em contraponto ao desemprego ou ocupaÃÃes desprestigiadas. Busco discutir como os meios de inserÃÃo, aprendizagem e sucesso no universo da tattoo refletem o tradicionalismo desse circuito bastante restrito, onde os neÃfitos devem ser iniciados nos saberes da prÃtica atravÃs da tutela de mestres reticentes em cultivar uma geraÃÃo mais jovem, dada a possibilidade de estarem formando possÃveis concorrentes. Indago ainda sobre a percepÃÃo que os profissionais tÃm sobre o prÃprio ofÃcio onde, apesar de reclamarem para si ideais de rebeldia e inconformismo, muitas vezes atuam de forma contrÃria aos valores que defendem, tanto nas formas de transmissÃo das tÃcnicas, quanto na sua adesÃo à lÃgica de mercado. / In recent decades, it has been observed that the practice of tattooing has acquired new forms and uses of social values, losing much of its aura of marginality, spreading with few restrictions of class, gender or age. Before means restricted to marginal, has recently become an object of consumption, widely announced, expanding its share of consumers demanding new sanitary procedures and transforming the office of tattooist in a lucrative occupation. From the field observations in three tattoo parlors in the city of Fortaleza, aboard the phenomenon by focusing on trajectories of six tattoo artists. The methodological procedures were semi-directed interviews with tattoo artists, informal conversations with customers and participant observation in the studios. The data collected suggest that tattoo artists mostly from the lower classes, are in the practice of tattooing a way to rise socially, avoiding occupations usually reserved for individuals with low education and come from humble families, emerging as a viable option as opposed to unemployment occupations or discredited. Busco discuss how the insertion means, learning and success in the world of tattoo reflects the traditionalism of this circuit very limited, where the neophytes should be initiated into the practice knowledge through the guidance of masters reluctant to cultivate a younger generation, given the possibility of are forming possible competitors. I inquired further about the perception that professionals have about the office itself where, although you claim to ideals of rebellion and nonconformity, often act in a manner contrary to the values they defend, both in the forms of transmission techniques, and in their adherence to market logic.

This study identified variations in the learning trajectories of Tier II students when learning equivalent fraction concepts using physical and virtual manipulatives. The study compared three interventions: physical manipulatives, virtual manipulatives, and a combination of physical and virtual manipulatives. The research used a sequential explanatory mixed-method approach to collect and analyze data and used two types of learning trajectories to compare and synthesize the results. For this study, 43 Tier II fifthgrade students participated in 10 sessions of equivalent fraction intervention. Pre- to postdata analysis indicated significant gains for all three interventions. Cohen d effect size scores were used to compare the effect of the three types of manipulatives—at the total, cluster, and questions levels of the assessments. Daily assessment data were used to develop trajectories comparing mastery and achievement changes over the duration of the intervention. Data were also synthesized into an iceberg learning trajectory containing five clusters and three subcluster concepts of equivalent fraction understanding and variations among interventions were identified. The syntheses favored the use of physical manipulatives for instruction in two clusters, the use of virtual manipulatives for one cluster, and the use of combined manipulatives for two clusters. The qualitative analysis identified variations in students’ resolution of misconceptions and variations in their use of strategies and representations. Variations favored virtual manipulatives for the development of symbolic only representations and physical manipulatives for the development of set model representations. Results also suggested that there is a link between the simultaneous linking of the virtual manipulatives and the development of multiplicative thinking as seen in the tendency of the students using virtual manipulative intervention to have higher gains on questions asking students to develop groups of three or more equivalent fractions. These results demonstrated that the instructional affordances of physical and virtual manipulatives are specific to different equivalent fraction subconcepts and that an understanding of the variations is needed to determine when and how each manipulative should be used in the sequence of instruction.

No description available.

The requirement to store and manipulate data that represents the location and extent of objects, like roads, cities, rivers, etc. (spatial data), led to the evolution of spatial database systems. The domains that led to an increased interest in spatial database systems are earth science, robotics, resource management, urban planning, autonomous navigation and geographic information systems (GIS). To handle the spatial data efficiently, spatial database systems require indexing mechanisms that can retrieve spatial objects based on their locations using direct look-ups as opposed to the sequential search. Indexing structures designed for relational database systems cannot be used for objects with non-zero size. The fact that there is no total ordering of objects in space makes the conventional indexes, such as the B+ tree, incapable of handling spatial data. / Extensive work has been done on spatial indexing and indexing methods are categorized in terms of their efficiency for the type of spatial objects or the type of queries. Queries in spatial database system are classified as single-scan and multi-scan queries. Spatial join is the most important multi-scan query in a spatial database system and the execution time of such queries is super linear to the number of objects. Among the indexing structures available for spatial join queries, Filter trees perform better than its counterparts, such as Hilbert R-trees. Filter tree join algorithm outperforms the R-tree join algorithm by reading each block of entities at most once. Filter trees combine the recursive partitioning, size separation and space filling curves to achieve this efficiency. However, for data sets of low join selectivity, the number of blocks processed for Filter trees is excessive compared to the number of blocks that have intersecting entities. / The goal of this work is to provide a method for accelerating spatial join operations by using Spatial Join Bitmap (SJB) indices. The file organization is based on the concepts introduced in Filter trees. The SJB indices keep track of blocks that have intersecting entities and make the algorithm process only those blocks. We provide algorithms for generating SJB indices dynamically and for maintaining SJB indices when the data sets are updated. Although maintaining SJB indices for updates increases the cost in terms of response time, the cost saving in terms of the join operation is substantial and this makes the overall behaviour of the spatial system very efficient. / We have performed an extensive study using both real and synthetic data sets of various data distributions. The results show that the use of SJB indices produces a substantial speed-up, ranging from 25% to 150% when compared to Filter trees. This method is highly beneficial in a real world scenario, as the number of times the data set is updated is fairly low when compared to the number of times the join processing is done on the data sets. / The spatial indexing structures can be extended to handle data of higher dimensions including time. The position of the geometries, like points, lines, areas or volumes changing over time, represents moving objects. The need for storing and processing moving object data arises in a wide range of applications, including digital battlefields (battlefield simulators), air-traffic control, and mobile communication systems. The successive locations of the object are gathered as the object moves around the space and the locations that are ordered in time are interpolated to obtain the movement of the object: this is called as trajectory of the object. R-tree variations, such as the three dimensional R-trees, TB-trees, FNR trees, STR trees, MON trees and SETI trees, are found to be effective for storing and manipulating past locations of moving objects. The SETI tree is a combination of the R-tree in the time dimension and the partition based technique in the space dimension, and outperforms the other R-tree indexing structures in handling coordinate based queries. However, SETI increases the computational time when handling trajectory queries that retrieve the whole or part of the trajectories. / We propose a methodology for using the recursive partitioning technique for indexing trajectories, called the Recursively Partitioned Trajectory Index (RPTI). RPTI uses a two-level indexing structure that is similar to the SETI and maintains separate indices for the space and time dimensions. However, the splitting of trajectory segments in SETI, which increases the computational time, does not arise in RPTI. We present the algorithms for constructing the RPTI and the algorithms for updates, which include insertion and deletion. We have conducted an experimental study of this method and have demonstrated that RPTI is better than SETI in handling trajectory queries and is competitive with SETI in handling coordinate based queries. Contrary to the SETI structure, RPTI recursively partitions the space and avoids the splitting of line segments, making it efficient for query processing. / Deletion is often ignored while proposing a trajectory index as a result of the assumption that deleting the trajectory of a moving object is meaningless after the transmitted positions are recorded. However, deletions are necessary when the trajectory of a moving object is no longer useful. We have also shown that deletion of a trajectory can be efficiently done using the RPTI structure. The structure of RPTI can be easily implemented by using any of the existing spatial indexing structures. The only design parameters required are the standard disk page size and maximum level of recursive partitioning. However, in SETI, the number of spatial partitions, which is a crucial parameter in any spatial partitioning strategy, is highly dependent on the distribution of data sets.

<p>This dissertation encompasses three essays which examine the development of obesity in black and white girls and its responses to interventions. </p><p>The first chapter asks the question, how does obesity develop in girls? Using the National Growth and Health Study (NGHS), a longitudinal study of 2400 girls from age 9 to age 18, this chapter aims to address gaps in knowledge about the development and persistence of obesity in girls. Analyses using multivariate regression and growth-mixture modeling describe trajectories of body mass change in children and their correlates. Results suggest that obesity in children begins early and persists in most cases--BMI at age 17 is, on average, 1.3 times BMI at age 9. However, change does occur; 0.8 percent of the sample move from being obese at age 9 to healthy weight at age 17, and 2.2 percent of the sample make the reverse journey from healthy weight to obese. Where change occurs, it is most commonly seen among those who socio-demographically were anomalies among their body mass cohort at age 9. These results emphasize the importance of early interventions as well as the need for more study into body mass mutability in population subsamples. </p><p>The second chapter investigates 1) what motivates children to pursue weight loss; and 2) what aspects of interventions may most effectively support healthy child motivations and program success. These questions are qualitatively studied among a sample of 45 obese girls aged 9 to 13 girls participating in a behavior modification intervention. In total, 106 interviews were conducted. All of the girls in the study were interested in losing weight, most commonly in order to fit in (n=11), reduce teasing (n=10), or express particular social identities (n=6). However, not all of the girls were able to translate this desire to lose weight into a healthy and effective lifestyle change motivation. Several factors were associated with adopting healthy motivation and behavior, including familial involvement, self-regulation skills, non-social weight desires, realistic weight loss goals, and clear messages about body ideals. Other program protocols also supported motivation during difficult periods for those who adopted healthy motivation, including nutrition information, incentives, lack of physician judgment, and patient autonomy. Finally, two other potential program protocols were mentioned by girls in the study as useful aids. More support services, particularly during the summer, and more information on the expected course of weight loss could, these girls argued, help sustain motivation. Together, these findings suggest a role for self-regulation theory in the design of lifestyle change motivation and for more directly addressing expectations in weight loss treatment.</p><p>The third chapter investigates the relationship between self-worth and obesity among girls, again using the National Growth and Health Study. Results indicate a negative relationship between self-worth and obesity across all participants. However, this relationship only has predictive power from early body mass to later self-worth and self-worth trajectories. That is, higher body mass at age 9 predicts lower self-worth at age 17 and decreases in self-worth from age 9 to age 17. The effect is larger for Caucasians and for those in young adolescence but persists across the sample. Mechanisms for this relationship are also investigated, and some support found for stigma. Analyses using self-worth components suggest most of the self-worth effects are driven by social concerns, while mediational analyses suggest social body image pressures explain the relationship between global self-worth and body mass. Overall, the findings suggest a complex interrelation between self-worth and body mass in girls, meriting further investigation as well as a more nuanced discussion in the public realm.</p> / Dissertation

<p>Despite decades of research attention given to academic underachievement, longitudinal and developmental investigation of this phenomenon has been sparse. To address this shortcoming, the current study used a longitudinal, person-centered approach to identify latent subgroups of growth in the joint development of underachievement and four motivational beliefs (self-concept, task importance, psychological cost value, and self-worth) from first through sixth grade. Two types of underachievement latent classes emerged: one characterized by sustained underachievement and the other by growing underachievement (an Achievement class was also consistently found). Sustained, chronic underachievement was not associated with declines in self-concept or task importance, but was related to moderately lower levels of psychological cost value and self-worth, and was also related to lower middle school academic achievement. Growing underachievement was associated with lower and declining self-concept and task importance. Although differential class membership by gifted status was hypothesized, no such effects were found. Gender effects were found for the Task Importance and Self-Worth models in the hypothesized direction, but this effect was not as robust as in prior research. Findings from the current study build on prior research highlighting heterogeneity among underachieving students.</p> / Dissertation

The purpose of this study was two-fold: (a) to identify, in a large representative sample of Canadian children, the age-related trajectories of overweight and obesity from toddlerhood into childhood and (b) to investigate the associations between these trajectories and children’s temperaments, their parents’ parenting practices and their interactions. Potentially important familial characteristics (i.e., the parents’ or surrogates’ age, income level, and educational attainment) were considered in the models. The sample for this study was drawn from the Canadian National Longitudinal Survey of Children and Youth (NLSCY). Group-based mixture modeling analyses were conducted to identify the number and types of distinct trajectories in the development of obesity (i.e., to explicate the developmental processes in the variability of childhood obesity) in a representative sample of children who were between 24 to 35 months of age, at baseline, and followed biennially over a 6-year span. Discriminant analysis was conducted to assess the theoretical notion of goodness-of-fit between parenting practices and children’s temperament, and their association with membership in the BMI trajectory groups. The results of the group-based modeling established three different BMI trajectories for the boys, namely: stable-normal BMI, transient-high BMI, and j-curve obesity. The analyses revealed four different trajectories of BMI change for the girls: stable-normal BMI, early-declining BMI, late-declining BMI, and accelerating rise to obesity. The multivariate analysis revealed that the combined predictors of the obesity trajectories of the girls (group membership) included having a fussy temperament, ineffective parenting, and parents’ educational attainment. Predictors of the boys’ obesity trajectory (group membership) included household income, parental education, and effective parenting practices. Understanding the different ways in which a child may develop obesity will allow nurses and other health professionals to take different approaches in the assessment, intervention and evaluation of obesity and obesity-related health problems. The results of this study further our understanding of factors associated with the development of obesity at a young age and hence may inform the development of early preventive programs.

No description available.

The de Broglie-Bohm causal interpretation of quantum mechanics is discussed, and applied to the hydrogen atom in several contexts. Prominent critiques of the causal program are noted and responses are given; it is argued that the de Broglie-Bohm theory is of notable interest to physics. Using the causal theory, electron trajectories are found for the conventional Schrödinger, Pauli and Dirac hydrogen eigenstates. In the Schrödinger case, an additional term is used to account for the spin; this term was not present in the original formulation of the theory but is necessary for the theory to be embedded in a relativistic formulation. In the Schrödinger, Pauli and Dirac cases, the eigenstate trajectories are shown to be circular, with electron motion revolving around the <i>z</i>-axis. Electron trajectories are also found for the 1<i>s</i>-2<i>p</i>0 transition problem under the Schrödinger equation; it is shown that the transition can be characterized by a comparison of the trajectory to the relevant eigenstate trajectories. The structures of the computed trajectories are relevant to the question of the possible evolution of a quantum distribution towards the standard quantum distribution (quantum equilibrium); this process is known as quantum relaxation. The transition problem is generalized to include all possible transitions in hydrogen stimulated by semi-classical radiation, and all of the trajectories found are examined in light of their implications for the evolution of the distribution to the standard distribution. Several promising avenues for future research are discussed.