50,869 research outputs found
Data Management Roles for Librarians
In this Chapter:● Looking at data through different lenses● Exploring the range of data use and data support ● Using data as the basis for informed decision making ● Treating data as a legitimate scholarly research produc
Investigation of the unsteady pressure distribution on the blade of an axial flow fan
A major source of the noise generated by high bypass ratio aircraft fan engines is the unsteady pressures (forces and moments) acting on the fan blades. These unsteady pressures are the result of the interaction of the blades with the wakes of upstream blade rows, inlet flow distortions, and inlet turbulence. An experimental system was developed which will permit the measurement of the unsteady pressure distributions; a series of experiments were conducted to investigate these effects, and the results are compared with predictions from existing theoretical analyses
Predicting species abundance distributions by simultaneously using number and biomass as units of measurement
The universal observation that some species in an ecological community are common, but many more are rare, is neatly encapsulated in a species abundance distribution (SAD)1. However, the shape of the distribution can depend on the currency used to measure abundance 2. Here we show how the SADs for numerical abundance and biomass are related and how this relationship can be used to predict the form of the SAD. When plotted in log numerical abundance, log biomass space, species points lie within an approximately triangular area the limits of which are set by body size range, and the upper limit of abundance in both metrics. Under the simplifying, but reasonable, assumption that the observed scatter of species within this region is random, the shape of the SAD is immediately derived from simple geometrical considerations. For the SAD of numerical abundance this is a power curve. The biomass SAD can be either a power curve or, more frequently, a unimodal curve, which can approximate a log normal. This log triangular random placement model serves as a null hypothesis against which actual communities can be compared. Data from two intensively surveyed local communities indicate that it can give a good approximation, with species scattered within a triangle. Further, we can predict the consequences, for the SAD, of size-selective sampling protocols. We argue that mechanistic models of SADs must be able to account for the relative abundance of species in alternative currencies. Moreover, this approach will shed light on niche packing and may have application in environmental monitoring
Gas chromatograph injection system
An injection system for a gas chromatograph is described which uses a small injector chamber (available in various configurations). The sample is placed in the chamber while the chamber is not under pressure and is not heated, and there is no chance of leakage caused by either pressure or heat. It is injected into the apparatus by changing the position of a valve and heating the chamber, and is volatilized and swept by a carrier gas into the analysis apparatus
Investigating the Potential of Fee-Based Recreation on Private Lands in the Lower Mississippi River Delta
Private landowners may be willing to allow public access for fee-based wildlife-associated recreation. A survey and econometric techniques are proposed to determine what characteristics may influence the probability to decide to offer recreation, what organizational form landowners may prefer to manage and market fee-based recreation, and how liability concerns and other possible disincentives collectively influence landowners' access decisions.wildlife-associated recreation, liability perceptions, Resource /Energy Economics and Policy,
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