Impact de la solidarité internationale sur la citoyenneté

National audienc

Turbulence kinetic energy equation for dilute suspensions

A multiphase turbulence closure model is presented which employs one transport equation, namely the turbulence kinetic energy equation. The proposed form of this equation is different from the earlier formulations in some aspects. The power spectrum of the carrier fluid is divided into two regions, which interact in different ways and at different rates with the suspended particles as a function of the particle-eddy size ratio and density ratio. The length scale is described algebraically. A mass/time averaging procedure for the momentum and kinetic energy equations is adopted. The resulting turbulence correlations are modeled under less retrictive assumptions comparative to previous work. The closures for the momentum and kinetic energy equations are given. Comparisons of the predictions with experimental results on liquid-solid jet and gas-solid pipe flow show satisfactory agreement

An examination of teacher migration in a large, urban school district

Teaching is professional work that as an occupation is characterized by many of the same rules of employment as other white-collar jobs. It is typically steady work with predictably rising pay, requires limited physical effort, a fixed amount of work time, and occurs in organizations that are rule-bound. Teaching is also uniquely complex, in that it requires a high degree of autonomy, responsibility for others, and extensive management activities. It is also work that has been the focus of significant public criticism for more than twenty-five years as students test scores have declined, the achievement gap among the races has widened, and student discipline problems have increased. Most importantly, it is work that is attracting fewer and fewer new entrants into its ranks at the same time it is losing teachers at a higher rate than other occupations. The purpose of this study was to better describe the complexity of the school staffing problem by examining teacher migration, one form of teacher turnover. The synthesis of research to date indicates that turnover destabilizes schools and that such instability has a direct effect on the success of students. Using quantitative and qualitative research methods, the personal characteristics of teachers who migrated during a four year period within the Duval County, Florida public schools were identified as were the organizational characteristics of the schools from which they migrated. Factors that influenced the decision to migrate were analyzed to determine the ways in which personal characteristics or school characteristics were associated with migration or influenced the decision to migrate. The findings of this study indicate that teachers migrated almost equally for personal reasons and because of the conditions and characteristics of the schools. Teachers migrated more frequently from poorer schools or lower-achieving schools due to an imbalance they experienced among the hard work that teaching in poorer schools takes, the time away from home that working so far away requires, and the kind and quality of administrative support that was received

Animation du séminaire ESO, Axe Parcours de vie et expériences des espaces

National audienc