Laminar flow: Challenge and potential

Commercial air transportation has experienced revolutionary technology advances since WWII. These technology advances have resulted in an explosive growth in passenger traffic. Today, however, many technologies have matured, and maintaining a similar growth rate will be a challenge. A brief history of laminar flow technology and its application to subsonic and supersonic air transportation is presented

An Altitude Chamber for the Study and Calibration of Aeronautical Instruments

The design and construction of an altitude chamber, in which both pressure and temperature can be varied independently, was carried out by the NACA at the Langley Memorial Aeronautical Laboratory for the purpose of studying the effects of temperature and pressure on aeronautical research instruments. Temperatures from +20c to -50c are obtained by the expansion of CO2from standard containers. The chamber can be used for the calibration of research instruments under altitude conditions simulating those up to 45,000 feet. Results obtained with this chamber have a direct application in the design and calibration of instruments used in free flight research

Interaction-tuned Anderson versus Mott localization

Disorder or sufficiently strong interactions can render a metallic state unstable causing it to turn into an insulating one. Despite the fact that the interplay of these two routes to a vanishing conductivity has been a central research topic, a unifying picture has not emerged so far. Here, we establish that the two-dimensional Falicov-Kimball model, one of the simplest lattice models of strong electron correlation does allow for the study of this interplay. In particular, we show that this model at particle-hole symmetry possesses three distinct thermodynamic insulating phases and exhibits Anderson localization. The previously reported metallic phase is identified as a finite-size feature due to the presence of weak localization. We characterize these phases by their electronic density of states, staggered occupation, conductivity, and the generalized inverse participation ratio. The implications of our findings for other strongly correlated systems are discussed.Comment: 5 pages, 4 figure

Spatially distributed water-balance and meteorological data from the Wolverton catchment, Sequoia National Park, California

Accurate water-balance measurements in the seasonal, snow-dominated Sierra Nevada are important for forest and downstream water management. However, few sites in the southern Sierra offer detailed records of the spatial and temporal patterns of snowpack and soil-water storage and the fluxes affecting them, i.e., precipitation as rain and snow, snowmelt, evapotranspiration, and runoff. To explore these stores and fluxes we instrumented the Wolverton basin (2180-2750 m) in Sequoia National Park with distributed, continuous sensors. This 2006-2016 record of snow depth, soil moisture and soil temperature, and meteorological data quantifies the hydrologic inputs and storage in a mostly undeveloped catchment. Clustered sensors record lateral differences with regards to aspect and canopy cover at approximately 2250 and 2625 m in elevation, where two meteorological stations are installed. Meteorological stations record air temperature, relative humidity, radiation, precipitation, wind speed and direction, and snow depth. Data are available at hourly intervals by water year (1 October-30 September) in non-proprietary formats from online data repositories (https://doi.org/10.6071/M3S94T)

Potato virus Y transmitting aphids in a Finnish seed potato area

The aphid-transmissible Potato virus Y is a major problem in seed potato production (Valkonen , 2007). The aphid flight activity was monitored from mid-June to the end of August with a suction trap and with yellow pan traps in 2007 and 2008. Previous studies have concluded that potato colonising aphids are not the main vectors of Potato virus Y

Self-control theory : an exploration of racial disparities in offending.

This study seeks to examine whether racial disparities in offending can be explained through self-control theory. The study utilized longitudinal responses of a nationally representative sample of 1700 adolescents. Parenting and self-control measures are taken from the mothers supplemental survey and peer pressure and offending are taken from self-reports from the adolescents at a later time. Structural equation modeling was used to examine the racial differences in self-control theory. Both a measurement model and a structural model are presented. The results of the study find empirical support for the construct of self-control theory, even within the face of racial disparities. However, support was not found for the link between race and parenting and therefore does not show support for self-control theory\u27s assumption that parenting can account for differences in offending across races. Both theoretical and policy implications are discussed

3D Geometric Morphometrics In Modern And Extinct Foot-Propelled Diving Birds: An Evaluation Of The Tarsometatarsus For Species Identification

Hesperornithiformes (Aves: Ornithurae) were flightless foot-propelled diving birds that lived during the Late Cretaceous and have a good fossil record compared to most Mesozoic birds. Extinct taxa are often identified using fragmentary or isolated specimens, and several species of Hesperornis have been named from the morphology of the tarsometatarsus, often relying on size for taxonomic differentiation. However, little has been done to examine intraspecific variation in this bone and evaluate its use for taxonomic identification. To test for intraspecific and interspecific variation in the tarsometatarsus of hesperornithiforms, variation in extant members of the foot-propelled diving Gaviidae (loons) and Podicipedidae (grebes) was considered. Loons and grebes are morphologically similar to extinct hesperornithiforms, making them appropriate analogues. Only adult female specimens were chosen for analysis to eliminate the possibility of sexual dimorphism or ontogenetic differences. Landmark-based Geometric Morphometrics was performed on 3D scans of specimens from three species per family, totaling 22 modern specimens. Five species of Hesperornis were scanned and analyzed, totaling 13 individuals. Separate analyses were performed on the shape of the full bone, the shape of the distal end, and the shape of the proximal end for each clade (Gaviidae, Podicipedidae, and Hesperornis). In nearly every Principal Component (PC) morphospace analysis of extant and extinct groups, individuals did not group by species, and any grouping that did occur was poorly defined. These results indicate that there is too much intraspecific variation and too little interspecific variation to confidently identify a species using only the tarsometatarsus in foot-propelled divers. Consequently, fossil hesperornithiform taxa described based on the tarsometatarsus alone may not be valid and require reevaluation

National Transonic Facility: A review of the operational plan

The proposed National Transonic Facility (NTF) operational plan is reviewed. The NTF will provide an aerodynamic test capability significantly exceeding that of other transonic regime wind tunnels now available. A limited number of academic research program that might use the NTF are suggested. It is concluded that the NTF operational plan is useful for management, technical, instrumentation, and model building techniques available in the specialized field of aerodynamic analysis and simulation. It is also suggested that NASA hold an annual conference to discuss wind tunnel research results and to report on developments that will further improve the utilization and cost effectiveness of the NTF and other wind tunnels