Reynolds and Mach number effects on multielement airfoils

Experimental studies were conducted to assess Reynolds and Mach number effects on a supercritical multielement airfoil. The airfoil is representative of the stall-critical station of an advanced transport wing design. The experimental work was conducted as part of a cooperative program between the Douglas Aircraft Company and the NASA LaRC to improve current knowledge of high-lift flows and to develop a validation database with practical geometries/conditions for emerging computational methods. This paper describes results obtained for both landing and takeoff multielement airfoils (four and three-element configurations) for a variety of Mach/Reynolds number combinations up to flight conditions. Effects on maximum lift are considered for the landing configurations and effects on both lift and drag are reported for the takeoff geometry. The present test results revealed considerable maximum lift effects on the three-element landing configuration for Reynolds number variations and significant Mach number effects on the four-element airfoil

Evolution to a smooth universe in an ekpyrotic contracting phase with w > 1

A period of slow contraction with equation of state w > 1, known as an ekpyrotic phase, has been shown to flatten and smooth the universe if it begins the phase with small perturbations. In this paper, we explore how robust and powerful the ekpyrotic smoothing mechanism is by beginning with highly inhomogeneous and anisotropic initial conditions and numerically solving for the subsequent evolution of the universe. Our studies, based on a universe with gravity plus a scalar field with a negative exponential potential, show that some regions become homogeneous and isotropic while others exhibit inhomogeneous and anisotropic behavior in which the scalar field behaves like a fluid with w=1. We find that the ekpyrotic smoothing mechanism is robust in the sense that the ratio of the proper volume of the smooth to non-smooth region grows exponentially fast along time slices of constant mean curvature.Comment: 8 pages, 5 figures; updated to coincide with published versio

Biodiversity Patterns of Littoral Tidal River Fishes in the Gulf Coastal Plain Region of Mississippi

Fish biodiversity patterns within littoral habitats of major tidal river systems of coastal Mississippi were examined. The biodiversity of littoral tidal river fishes varied meaningfully on several spatial scales in the Gulf Coastal Plain region of Mississippi. Fish diversity typically appeared higher in littoral channel habitats than in side-pond habitats of tidal river systems. Faunal representation by three core groups of littoral fishes (cyprinids, centrarchids, and fundulids) generally differed between side-pond and channel habitats, as well as among different tidal river systems. Some of the faunal variation among systems reflected biogeographic (east/west) trends, but most of the variation reflected system size-related patterns. Among-site similarity in fish assemblage composition reflected both site proximity and system size. Moreover, the degree of variability in assemblage composition increased with system size. Thus, regional assemblage patterns were generally most discernible on the landscape scale, rather than through historical congruence. This limited regional study of tidal river fish biodiversity improved our biogeographic understanding by revealing the importance of landscape-scale factors such as tidal river size and associated variation in the available species pool. Understanding landscape-scale environmental variation is key to explaining regional fish diversity patterns

A Lyman alpha halo around a quasar at redshift z=6.4

We present long-slit spectroscopic data which reveals extended Lyman alpha emission around the z=6.417 radio-quiet quasar CFHQS J2329-0301. The Lyman alpha emission is extended over 15 kpc and has a luminosity of > 8 x 10^36 W, comparable to the most luminous Lyman alpha halos known. The emission has complex kinematics, in part due to foreground absorption which only partly covers the extended nebula. The velocity ranges from -500 km/s to +500 km/s, with a peak remarkably close to the systemic velocity identified by broad MgII emission of the quasar. There is no evidence for infall or outflow of the halo gas. We speculate that the Lyman alpha emission mechanism is recombination after quasar photo-ionization of gas sitting within a high-mass dark matter halo. The immense Lyman alpha luminosity indicates a higher covering factor of cold gas compared to typical radio-quiet quasars at lower redshift.Comment: 7 pages, 7 figures, AJ, in pres

Independent Orbiter Assessment (IOA): Assessment of the orbital maneuvering system FMEA/CIL, volume 1

The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA effort first completed an analysis of the Orbital Maneuvering System (OMS) hardware and Electrical Power Distribution and Control (EPD and C), generating draft failure modes and potential critical items. To preserve independence, this analysis was accomplished without reliance upon the results contained within the NASA FMEA/CIL documentation. The IOA results were then compared to the proposed Post 51-L NASA FMEA/CIL baseline. This report documents the results of that comparison for the Orbiter OMS hardware. The IOA analysis defined the OMS as being comprised of the following subsystems: helium pressurization, propellant storage and distribution, Orbital Maneuvering Engine, and EPD and C. The IOA product for the OMS analysis consisted of 284 hardware and 667 EPD and C failure mode worksheets that resulted in 160 hardware and 216 EPD and C potential critical items (PCIs) being identified. A comparison was made of the IOA product to the NASA FMEA/CIL baseline which consisted of 101 hardware and 142 EPD and C CIL items

Selection Tool Use: A Focus on Personality Testing in Canada, the United States, and Germany

The purpose of this paper is to provide new data regarding the current staffing practices being used by organizations in Canada and the United States (US) as well as a comparison with existing data from Germany (Diekmann & König, 2015). Data regarding the beliefs of human resource (HR) practitioners in terms of using personality tests in personnel selection is also provided. A geographically representative sample of 453 HR practitioners across Canada and the US were surveyed. Although general mental ability testing has previously been found to be highly valid and cost effective, this selection tool was among the least commonly used in all three countries. Personality tests were also rarely used (especially in Canada and the US) and research–practice gaps still appear to be an issue (e.g., HR practitioners’ preference for personality types as opposed to traits)

Asymptotic silence-breaking singularities

We discuss three complementary aspects of scalar curvature singularities: asymptotic causal properties, asymptotic Ricci and Weyl curvature, and asymptotic spatial properties. We divide scalar curvature singularities into two classes: so-called asymptotically silent singularities and non-generic singularities that break asymptotic silence. The emphasis in this paper is on the latter class which have not been previously discussed. We illustrate the above aspects and concepts by describing the singularities of a number of representative explicit perfect fluid solutions.Comment: 25 pages, 6 figure