Population potential in Metropolitan areas

Thesis (M.C.P.) Massachusetts Institute of Technology. Dept. of City and Regional Planning, 1949.Bibliography: leaf 20.by Richard Wellborn Roether.M.C.P

Channel Catfish Life History and Biology.

4 p

Construction of Levee-type Ponds for Fish Production.

4 p

Site Selection of Levee-type Fish Production Ponds.

2 p

Effects of shrouded stator cavity flows on multistage axial compressor aerodynamic performance

Experiments were performed on a low-speed multistage axial-flow compressor to assess the effects of shrouded stator cavity flows on aerodynamic performance. Five configurations, which involved changes in seal-tooth leakage rates and/or elimination of the shrouded stator cavities, were tested. Data collected enabled differences in overall, individual stage and the third stage blade element performance parameters to be compared. The results show conclusively that seal-tooth leakage can have a large impact on compressor aerodynamic performance while the presence of the shrouded stator cavities alone seemed to have little influence. Overall performance data revealed that for every 1% increase in the seal-tooth clearance to blade-height ratio the pressure rise dropped up to 3% while efficiency was reduced by 1 to 1.5 points. These observed efficiency penalty slopes are comparable to those commonly reported for rotor and cantilevered stator tip clearance variations. Therefore, it appears that in order to correctly predict overall performance it is equally important to account for the effects of seal-tooth leakage as it is to include the influence of tip clearance flows. Third stage blade element performance data suggested that the performance degradation observed when leakage was increased was brought about in two distinct ways. First, increasing seal-tooth leakage directly spoiled the near hub performance of the stator row in which leakage occurred. Second, the altered stator exit flow conditions caused by increased leakage impaired the performance of the next downstream stage by decreasing the work input of the downstream rotor and increasing total pressure loss of the downstream stator. These trends caused downstream stages to progressively perform worse;Other measurements were acquired to determine spatial and temporal flow field variations within the up-and-downstream shrouded stator cavities. Flow within the cavities involved low momentum fluid traveling primarily in the circumferential direction at about 40% of the hub wheel speed. Measurements indicated that the flow within both cavities was much more complex than first envisioned. A vortical flow structure in the meridional plane, similar to a driven cavity, existed within the upstream cavity. Furthermore, other spatial and temporal variations in flow properties existed, the most prominent being caused by the upstream potential influence of the downstream blade. This influence caused the fluid within cavities near the leading edges of either stator blades in space or rotor blades in time to be driven radially inward relative to fluid near blade mid-pitch. This influence also produced large unsteady velocity fluctuations in the downstream cavity because of the passing of the downstream rotor blade

DESCRIPTION OF THE PRACTICE HISTORIES AND KNOWLEDGE STRUCTURES OF HIGH SCHOOL BASEBALL PLAYERS

Early specialization (Ericsson, et al., 1993) and early diversification (Cote, 1999) are two highly debated approaches to the development of elite sport performance. More research is needed to determine the types of practice that aid in the development of elite sport performance. Further, studies describing the practice and competition histories of high school baseball players are needed to determine the role of early specialization and non-specialization in the development of baseball players between the ages of 14 and 18. Two studies were conducted. The purpose of the first study was to determine whether predictions from early specialization (deliberate practice, Ericsson, et al., 1993) or the early diversification (sampling a variety of sports, Cote, 1999) more accurately described the practice history of high school baseball players. Retrospective interviews (Cote, Ericsson & Law, 2005) were used to collect information related to participants’ developmental histories. Participants (n=51) began at an early age (5) and were playing year round for multiple baseball teams by age 10. In addition, total accumulated hours of practice for these high school players were similar to the hours for a different sample of high school players (Cathey, 2010). After 10 years involvement (between the ages of 5 and 14), players had accumulated an average of 3,200 practice hours. Similar patterns of practice and early engagement maybe necessary to become a successful high school baseball player. Results supported a trend toward early specialization and accumulation of deliberate practice (Ericsson, et al., 1993)