Optimum Multi-Impulse Rendezvous Program

OMIRPROGRAM determines optimal n-impulse rendezvous trajectories under the restrictions of two-body motion in free space. Lawden's primer vector theory is applied to determine optimum number of midcourse impulse applications. Global optimality is not guaranteed

Natural laminar flow flight experiments on a swept wing business jet-boundary layer stability analyses

The linear boundary layer stability analyses and their correlation with data of 18 cases from a natural laminar flow (NLF) flight test program using a Cessna Citation 3 business jet are described. The transition point varied from 5% to 35% chord for these conditions, and both upper and lower wing surfaces were included. Altitude varied from 10,000 to 43,000 ft and Mach number from 0.3 to 0.8. Four cases were at nonzero sideslip. Although there was much scatter in the results, the analyses of boundary layer stability at the 18 conditions led to the conclusion that crossflow instability was the primary cause of transition. However, the sideslip cases did show some interaction of crossflow and Tollmien-Schlichting disturbances. The lower surface showed much lower Tollmien-Schlichting amplification at transition than the upper surface, but similar crossflow amplifications. No relationship between Mach number and disturbance amplification at transition could be found. The quality of these results is open to question from questionable wing surface quality, inadequate density of transition sensors on the wing upper surface, and an unresolved pressure shift in the wing pressure data. The results of this study show the need for careful preparation for transition experiments. Preparation should include flow analyses of the test surface, boundary layer disturbance amplification analyses, and assurance of adequate surface quality in the test area. The placement of necessary instruments and usefulness of the resulting data could largely be determined during the pretest phase

F-111 natural laminar flow glove flight test data analysis and boundary layer stability analysis

An analysis of 34 selected flight test data cases from a NASA flight program incorporating a natural laminar flow airfoil into partial wing gloves on the F-111 TACT airplane is given. This analysis determined the measured location of transition from laminar to turbulent flow. The report also contains the results of a boundary layer stability analysis of 25 of the selected cases in which the crossflow (C-F) and Tollmien-Schlichting (T-S) disturbance amplification factors are correlated with the measured transition location. The chord Reynolds numbers for these cases ranges from about 23 million to 29 million, the Mach numbers ranged from 0.80 to 0.85, and the glove leading-edge sweep angles ranged from 9 deg to 25 deg. Results indicate that the maximum extent of laminar flow varies from 56% chord to 9-deg sweep on the upper surface, and from 51% chord at 16-deg sweep to 6% chord at 25-deg sweep on the lower. The results of the boundary layer stability analysis indicate that when both C-F and T-S disturbances are amplified, an interaction takes place which reduces the maximum amplification factor of either type of disturbance that can be tolerated without causing transition

High Reynolds number tests of a Boeing BAC I airfoil in the Langley 0.3-meter transonic cryogenic tunnel

A wind tunnel investigation of an advanced-technology airfoil was conducted in the Langley 0.3-Meter Transonic Cryogenic Tunnel (TCT). This investigation represents the first in a series of NASA/U.X. industry two dimensional airfoil studies to be completed in the Advanced Technology Airfoil Test program. Test temperature was varied from ambient to about 100 K at pressures ranging from about 1.2 to 6.0 atm. Mach number was varied from about 0.40 to 0.80. These variables provided a Reynolds number (based on airfoil chord) range from about .0000044 to .00005. This investigation was specifically designed to: (1) test a Boeing advanced airfoil from low to flight-equivalent Reynolds numbers; (2) provide the industry participant (Boeing) with experience in cryogenic wind-tunnel model design and testing techniques; and (3) demonstrate the suitability of the 0.3-m TCT as an airfoil test facility. All the objectives of the cooperative test were met. Data are included which demonstrate the effects of fixed transition, Mach number, and Reynolds number on the aerodynamic characteristics of the airfoil. Also included are remarks on the model design, the model structural integrity, and the overall test experience

The effect of advertising on children and adolescents

In 100 years, marketing to children went from a severely frowned upon practice to an integral part of growing up as companies came to realize that investing in marketing to children and adolescents provides excellent immediate and future dividends. Each year, enormous sums of money are spent to reach this valuable audience because children and adolescents spend billions on their own purchases, influence family decisions about what to buy, and promise a potential lifetime of brand loyalty. The channels to reach youth have grown, and marketers are increasingly using them, often blurring the distinction between entertainment and advertising. Because advertising to children and adolescents has become ubiquitous, researchers who study its influence raise significant concerns about the practice, especially as it relates to dietary behavior, family conflict, marketer tactics, and children's potential vulnerability as an audience. In this review by the Workgroup on Marketing and Advertising, we highlight the state of the research in this area and suggest that more research needs to be conducted on understanding the following: the effects of advertising exposure, how psychological development affects children's responses to marketing, the problems associated with advertising in newer media, and how researchers, parents, and practitioners might be able to mitigate the most deleterious advertising effects. We then present avenues of future research along with recommendations for key stakeholders.</p

The effect of advertising on children and adolescents

In 100 years, marketing to children went from a severely frowned upon practice to an integral part of growing up as companies came to realize that investing in marketing to children and adolescents provides excellent immediate and future dividends. Each year, enormous sums of money are spent to reach this valuable audience because children and adolescents spend billions on their own purchases, influence family decisions about what to buy, and promise a potential lifetime of brand loyalty. The channels to reach youth have grown, and marketers are increasingly using them, often blurring the distinction between entertainment and advertising. Because advertising to children and adolescents has become ubiquitous, researchers who study its influence raise significant concerns about the practice, especially as it relates to dietary behavior, family conflict, marketer tactics, and children's potential vulnerability as an audience. In this review by the Workgroup on Marketing and Advertising, we highlight the state of the research in this area and suggest that more research needs to be conducted on understanding the following: the effects of advertising exposure, how psychological development affects children's responses to marketing, the problems associated with advertising in newer media, and how researchers, parents, and practitioners might be able to mitigate the most deleterious advertising effects. We then present avenues of future research along with recommendations for key stakeholders.</p

Incidence and survival rate of women with cervical cancer in the Greater Amsterdam area

To evaluate the effect of population-based cervical cancer screening on the occurrence of cervical cancer in The Netherlands, we investigated the incidence and survival of cervical cancer registered by a cancer registry in the Greater Amsterdam area. The incidence rate of squamous cell carcinoma decreased significantly from 9.2/100,000 women in 1988 to 5.9/100,000 in 2000 (P<0.001). The incidence rate of adenocarcinomas remained stable. After adjustment for age, stage and lymph node involvement, the relative risk of death was 1.6 times higher for patients with adenocarcinomas than for patients with squamous cell carcinoma (95% CI 1.2-2.1). The decreased survival was related to histological type, as the effect remained significant after correction for confounding factors. Over time, the prognosis of women with squamous cell carcinoma improved significantly. No significant change was observed for women diagnosed with adenocarcinoma. These results suggest that the screening programme in The Netherlands as executed in the Greater Amsterdam area is associated with a decreased incidence and increased survival of patients with squamous cell carcinoma, but fails to detect (pre)malignant lesions of adenocarcinoma. Since more than 92% of adenocarcinomas and its precursors contain high-risk HPV, adding HPV testing to cytologic screening might improve the present screening programme in detecting adenocarcinoma and its precursor lesions