31,987 research outputs found
Map projections for larger-scale mapping
For the U.S. Geological Survey maps at 1:1,000,000-scale and larger, the most common projections are conformal, such as the Transverse Mercator and Lambert Conformal Conic. Projections for these scales should treat the Earth as an ellipsoid. In addition, the USGS has conceived and designed some new projections, including the Space Oblique Mercator, the first map projection designed to permit low-distortion mapping of the Earth from satellite imagery, continuously following the groundtrack. The USGS has programmed nearly all pertinent projection equations for inverse and forward calculations. These are used to plot maps or to transform coordinates from one projection to another. The projections in current use are described
Electrophoresis device
A device for separating cellular particles of a sample substance into fractionated streams of different cellular species includes a casing having a distribution chamber, a separation chamber, and a collection chamber. The electrode chambers are separated from the separation chamber interior by means of passages such that flow variations and membrane variations around the slotted portion of the electrode chamber do not enduce flow perturbations into the laminar buffer curtain flowing in the separation chamber. The cellular particles of the sample are separated under the influence of the electrical field and the separation chamber into streams of different cellular species. The streams of separated cells enter a partition array in the collection chamber where they are fractionated and collected
Three-dimensional laser Doppler anemometer measurements of a jet in a crossflow
A three-dimensional laser Doppler anemometer (3D-LDA) was used in a wind tunnel to measure a jet in a crossflow. Measurements were made in the vicinity of a 5-cm-diam jet which issued normally into a 10.65 m/sec wind tunnel crossflow; the velocity ratio Vjet/Vinf was 8. Detailed lateral surveys were made at two elevations (z = cm and 2 cm); both elevations were within the region affected by the boundary layer on the plate. The results are believed to provide reliable velocity field information in the boundary layer of the jet in a crossflow. Turbulence information also is available and believed to be roughly correct, although it may be subject to broadening effects for the lower values of turbulence. A weak vortex pair was observed in the wake at the plate surface. This structure existed in the boundary layer and built confidence because the 3D-LDA was, indeed, able to resolve fine detail in the wake. The capabilities of the 3D-LDA not only allow the making of the velocity surveys, but can be utilized to follow mean streamlines in the flow
Using a 3-dimensional laser anemometer to determine mean streamline patterns in a turbulent flow
The determination of mean streamline patterns by moving the test point in the direction of the measured velocity is shown to produce cumulative errors that are unacceptable. A two-dimensional algorithm that minimizes these errors is presented and is analytically validated using simple potential flows. The algorithm is extended to three-dimensional flows and is again validated analytically. Finally, as an example of a typical application of the algorithm, mean streamlines are measured in a complex, turbulent flow with a three-dimensional laser anemometer
An algorithm for using a laser anemometer to determine mean streamline patterns in a turbulent flow
The technique of tracing out a mean flow streamline with a three dimensional laser Doppler anemometer (LDA) is discussed with respect to cumulative, systematic errors that are inherent when the motion of the LDA test point is in the direction of the local measured velocity. Using simple potential flows that have variable curvature and inflection points to simulate an LDA experiment, a streamline tracing algorithm is developed that minimizes these errors. Also, the test point path remains close to the correct streamline even when simulated statistical measurement variations are included
A Search for Biomolecules in Sagittarius B2 (LMH) with the ATCA
We have used the Australia Telescope Compact Array to conduct a search for
the simplest amino acid, glycine (conformers I and II), and the simple chiral
molecule propylene oxide at 3-mm in the Sgr B2 LMH. We searched 15 portions of
spectrum between 85 and 91 GHz, each of 64 MHz bandwidth, and detected 58
emission features and 21 absorption features, giving a line density of 75
emission lines and 25 absorption lines per GHz stronger than the 5 sigma level
of 110 mJy. Of these, 19 are transitions previously detected in the
interstellar medium, and we have made tentative assignments of a further 23
features to molecular transitions. However, as many of these involve molecules
not previously detected in the ISM, these assignments cannot be regarded with
confidence. Given the median line width of 6.5 km/s in Sgr B2 LMH, we find that
the spectra have reached a level where there is line confusion, with about 1/5
of the band being covered with lines. Although we did not confidently detect
either glycine or propylene oxide, we can set 3 sigma upper limits for most
transitions searched. We also show that if glycine is present in the Sgr B2 LMH
at the level of N = 4 x 10^{14} cm^{-2} found by Kuan et al. (2003) in their
reported detection of glycine, it should have been easily detected with the
ATCA synthesized beam size of 17.0 x 3.4 arcsec^{2}, if it were confined to the
scale of the LMH continuum source (< 5 arcsec). This thus puts a strong upper
limit on any small-scale glycine emission in Sgr B2, for both of conformers I
and II.Comment: 12 pages, 2 figures, 5 tables, accepted by MNRA
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