75,539 research outputs found
Pretreatment method for anti-wettable materials
Anti-wettable materials brazing processes using titanium and zirconium for surface pretreatmen
The quiescent progenitors of four Type II-P/L supernovae
We present Large Binocular Telescope difference imaging data for the final
years of four Type II-P/L supernovae progenitors. For all four, we find no
significant evidence for stochastic or steady variability in the U, B, V, or
R-bands. Our limits constrain variability to no more than roughly 5-10% of the
expected R-band luminosities of the progenitors. These limits are comparable to
the observed variability of red supergiants in the Magellanic Clouds. Based on
these four events, the probability of a Type II-P/L progenitor having an
extended outburst after Oxygen ignition is <37% at 90% confidence. Our
observations cannot exclude short outbursts in which the progenitor returns to
within ~10% of its quiescent flux on the time scale of months with no dust
formation.Comment: 9 pages, 8 figures, 1 table. Accepted to MNRA
Experimental effects of fuselage camber on longitudinal aerodynamic characteristics of a series of wing-fuselage configurations at a Mach number of 1.41
An experimental investigation was conducted to evaluate a method for the integration of a fighter-type fuselage with a theoretical wing to preserve desirable wing aerodynamic characteristics for efficient maneuvering. The investigation was conducted by using semispan wing fuselage models mounted on a splitter plate. The models were tested through an angle of attack range at a Mach number of 1.41. The wing had a leading edge sweep angle of 50 deg and an aspect ratio of 2.76; the wing camber surface was designed for minimum drag due to lift and was to be self trimming at a lift coefficient of 0.2 and at a Mach number of 1.40. A series of five fuselages of various camber was tested on the wing
Stellar Mergers Are Common
The observed Galactic rate of stellar mergers or the initiation of common
envelope phases brighter than M_V=-3 (M_I=-4) is of order 0.5 (0.3)/year with
90% confidence statistical uncertainties of 0.24-1.1 (0.14-0.65) and factor of
2 systematic uncertainties. The (peak) luminosity function is roughly dN/dL
L^(-1.4+/-0.3), so the rates for events more luminous than V1309 Sco (M_V=-7
mag) or V838Mon (M_V=-10 mag) are lower at r~0.1/year and 0.03/year,
respectively. The peak luminosity is a steep function of progenitor mass, L
M^(2-3). This very roughly parallels the scaling of luminosity with mass on the
main sequence, but the transients are ~2000-4000 times more luminous at peak.
Combining these, the mass function of the progenitors, dN/dM M^(-2.0+/-0.8), is
consistent with the initial mass function, albeit with broad uncertainties.
These observational results are also broadly consistent with the estimates of
binary population synthesis models. While extragalactic variability surveys can
better define the rates and properties of the high luminosity events,
systematic, moderate depth (I>16 mag) surveys of the Galactic plane are needed
to characterize the low luminosity events. The existing Galactic samples are
only ~20% complete and Galactic surveys are (at best) reaching a typical
magnitude limit of <13 mag.Comment: Submitted to MNRAS (13 pages, 6 figures, 3 tables
The remote sensing of aquatic macrophytes Part 1: Color-infrared aerial photography as a tool for identification and mapping of littoral vegetation. Part 2: Aerial photography as a quantitative tool for the investigation of aquatic ecosystems
Research was initiated to use aerial photography as an investigative tool in studies that are part of an intensive aquatic ecosystem research effort at Lake Wingra, Madison, Wisconsin. It is anticipated that photographic techniques would supply information about the growth and distribution of littoral macrophytes with efficiency and accuracy greater than conventional methods
Semianalytic modeling of aerodynamic shapes
Equations for the semianalytic representation of a class of surfaces that vary smoothly in cross-sectional shape are presented. Some methods of fitting together and superimposing such surfaces are described. A brief discussion is also included of the application of the theory in various contexts such as computerized lofting of aerodynamic surfaces and grid generation
Improving the Efficiency of Wildlife Management: An Application to Waterfowl Production in the Prairie Pothole Region
Wildlife management agencies increasingly use economic analyses to improve the efficiency of their management policies. Few economic studies consider supply-side analyses for wildlife management, due, in part, to a lack of biological response data that capture the full range of management strategies and the influence of landscape characteristics. This paper uses a simulation model to generate biological response functions, which are then embedded within an economic model to determine least cost management strategies. The procedure is applied to waterfowl management in the Prairie Pothole Region of the northern Great Plains. Results highlight management inefficiencies that result from oversimplified response functions that do not account for non-linear relationships or spatial heterogeneity. Results also indicate that intensive management activities, which are generally compatible with agricultural land use, are a cost effective means of achieving waterfowl population objectives. This has important implications for the tradeoff between agricultural and waterfowl production in the Prairie Pothole Region.Resource /Energy Economics and Policy,
On the Marginal Value of a Fish: Some Evidence from a Steelhead Fishery
Policymakers and other interested parties frequently request information on the recreational value of a fish. Although fishing valuation studies date back at least 25 years, most studies focus on the average value of a fish. If the purpose of such estimates is to measure the value of incremental changes in fish numbers, then use of average estimates may lead to an incorrect policy decisions. The objective of this analysis is to estimate the marginal value of a steelhead trout in a recreational fishery on the John Day River of Oregon. The study uses contingent valuation procedures to elicit willingness to pay estimates for improvements in fish numbers and success rates. For the anglers in this survey, the value of an additional steelhead is $6.65 under current catch conditions. This value is much lower than values currently used in public debates in the Pacific Northwest, but similar to some marginal values reported in the recent literature. Implications of these values relative to average values are discussed.Demand and Price Analysis, Environmental Economics and Policy, Research Methods/ Statistical Methods, Resource /Energy Economics and Policy,
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