Search

Compared to Whites and Asian Americans, African Americans, Latinos, and Native Americans are severely under represented among top students in the United States at all levels of the educational system. This longstanding pattern is documented by virtually every traditional measure of academic achievement, including GPA, class rank, and standardized test scores. Moreover, all social class segments of these groups are underrepresented among the nation's top students. For example, this is the case for students from these groups who have parents who have not completed high school and for students with parents who have graduate and professional degrees. Over the years, relatively little attention has been given to increasing the number of top Black, Hispanic, and Native American students, which helps explain why there are very few strategies at any level of the educational system with strong empirical evidence that they can increase the number of high achieving students from these groups on a widespread basis. If there is to be sustained progress in this area, it probably will be necessary to give considerable priority over the next 10-20 years (and beyond) to the design, testing, and rigorous evaluation of strategies that are explicitly concerned with increasing the number of top students from these groups. To pursue this agenda effectively, it is recommended that several new entities be created that would each specialize in one or two important aspects of the high achievement challenge. For example, an entity should be created that would be concerned with developing model preschool and parent education programs that could improve the school readiness of middle and high SES youngsters from underrepresented groups, while another entity should be created that would specialize in evaluating programs and strategies at the higher education level that serve underrepresented minority students to determine if they help increase the number of top students from these groups in higher education. It also is recommended that these entities be mainly new nonprofit organizations or university-based centers, in order to ensure that they have the freedom and independence to maintain their specialized agendas over time.

This article examines the challenges associated with improving outcomes in higher education for Latino students. The author reviews data on the underrepresentation of Latinos among top high school students and among top undergraduate students. A discussion of the lack of strategies for increasing the number of high-achieving Hispanic students on the undergraduate level is presented along with a review of strategies that are being developed to increase the number of high achieving Latino undergraduates.

A new nonintrusive flow diagnostics instrumentation system, Doppler global velocimetry, is presented. The system is capable of making simultaneous, three-component velocity measurements within a selected measurement plane at video camera rates. These velocity images can provide the researcher with spatial and temporal information about the flow field in a global sense. The investigation of a vortical flow above a 75-degree delta wing comparing standard three-component, fringe-type laser velocimetry measurements with Doppler global velocimetry measurements is presented.

A new measurement technique, Doppler global velocimetry, has been described along with results from an experimental investigation of a vortical flow field. The results of this investigation, when compared to conventional laser velocimeter measurements, indicate that this technique is capable of describing the global velocity field within a measurement plane in real time. Further investigations are being conducted to correct the deficiencies described and to refine the measurement technique for flight applications.

A review of Doppler Global Velocimetry (DGV) data obtained during wind tunnel tests on a 75 degree swept delta wing was performed. High frequency variations observed in normalized data files are attributed to image alignment problems. Unfortunately, initial DGV velocity data compared poorly with baseline reference data. Nonlinear DGV system operation during the tests is the likely source of this problem. Corrected data compares much more favorably and suggests that DGV is a valid measurement technique. Future DGV investigations should include a method or means for monitoring laser frequency relative to the ALF transfer function behavior.

A new measurement technique is being developed by NASA to measure off-surface flow fields. This method, Doppler global velocimetry, will allow quantification of complex three-dimensional flow fields at video camera rates. The entire flow field structure within a selected plane is measured simultaneously rather than by scanned, point-by-point measurements using conventional laser velocimetry. Data obtained using this technique will be used to correlate with other data sets for verification, and following verification, provide a quantified, highly detailed definition of the flow field. This will help to improve the understanding of fluid physics, supplement and broaden the database required to validate and refine computational fluid dynamics (CFD) models, and improve aircraft design methodology. To assess the capability of the technique, velocity measurements of the vortical flow field above a thin 75-degree delta wing were made in the NASA - Langley Basic Aerodynamics Research Tunnel. Preliminary comparisons of the results were made with similar measurements obtained using a three component laser velocimeter indicate that this technique is capable of describing the entire three - component velocity flow field simultaneously within a measurement plane in real time.

A new velocimetry system is currently being developed at NASA LaRC. The device, known as a Doppler global velocimeter (DGV), can record three velocity components within a plane simultaneously and in near real time. To make measurements the DGV, like many other velocimetry systems, relies on the scattering of light from numerous small particles in a flow field. The particles or seeds are illuminated by a sheet of laser light and viewed by two CCD cameras. The scattered light from the particles will have a frequency which is a function of the source laser light frequency, the viewing angle, and most importantly the seed velocities. By determining the scattered light intensity the velocity can be measured at all points within the light sheet simultaneously. Upon completion of DGV component construction and initial check out a series of tests in the Basic Aerodynamic Research (wind) Tunnel (BART) are scheduled to verify instrument operation and accuracy. If the results are satisfactory, application of the DGV to flight measurements on the F-18 High Alpha Research Vehicle (HARV) are planned. The DGV verification test in the BART facility will utilize a 75 degree swept delta wing model. A major task undertaken this summer included evaluation of previous results for this model. A specific series of tests matching exactly the previous tests and exploring new DGV capabilities were developed and suggested. Another task undertaken was to study DGV system installation possibilities in the F-18 HARV aircraft. In addition, a simple seeding system modification was developed and utilized to make Particle Imaging Velocimetry (PIV) measurements in the BART facility.