28,261 research outputs found
Directly comparing coronal and solar wind elemental fractionation
As the solar wind propagates through the heliosphere, dynamical processes
irreversibly erase the signatures of the near-Sun heating and acceleration
processes. The elemental fractionation of the solar wind should not change
during transit however, making it an ideal tracer of these processes. We aimed
to verify directly if the solar wind elemental fractionation is reflective of
the coronal source region fractionation, both within and across different solar
wind source regions. A backmapping scheme was used to predict where solar wind
measured by the Advanced Composition Explorer (ACE) originated in the corona.
The coronal composition measured by the Hinode Extreme ultraviolet Imaging
Spectrometer (EIS) at the source regions was then compared with the in-situ
solar wind composition. On hourly timescales there was no apparent correlation
between coronal and solar wind composition. In contrast, the distribution of
fractionation values within individual source regions was similar in both the
corona and solar wind, but distributions between different sources have
significant overlap. The matching distributions directly verifies that
elemental composition is conserved as the plasma travels from the corona to the
solar wind, further validating it as a tracer of heating and acceleration
processes. The overlap of fractionation values between sources means it is not
possible to identify solar wind source regions solely by comparing solar wind
and coronal composition measurements, but a comparison can be used to verify
consistency with predicted spacecraft-corona connections.Comment: Accepted version; 8 pages, 7 figure
Basic hydrogeologic and remote sensing data for selection of sanitary landfill sites
Solid waste disposal were studied in Volusia County to protect the water supply in the area. Highlands in this County are of limited areal extent and, most significantly, the sand hills and ridges are in areas where recharge of the Floridan aquifer occurs. This study proves that well drained soils meeting the current State requirements are of limited areal extent. These areas should not be utilized as sanitary landfill sites! Rather, it is recommended that the Tomoka Farm Road site into the adjacent wetlands be extended. The County site on Rima Ridge recommended by Greenleaf-Telesca as the primary waste burial site in the County should be re-evaluated because of potential danger to the Daytona Beach water supply
Evaluation of the utility of sediment data in NASQAN (National Stream Quality Accounting Network)
Monthly suspended sediment discharge measurements, made by the USGS as part of the National Stream Quality Accounting Network (NASQAN), are analysed to assess the adequacy in terms of spatial coverage, temporal sampling frequency, accuracy of measurements, as well as in determining the sediment yield in the nation's rivers.
It is concluded that the spatial distribution of NASQAN stations is reasonable but necessarily judgemental. The temporal variations of sediment data contain much higher frequencies than monthly. Sampling error is found to be minor when compared with other causes of data scatter which can be substantial. The usefulness of the monthly measurements of sediment transport is enhanced when combined with the daily measurements of water discharge. Increasing the sampling frequency moderately would not materially improve the accuracy of sediment yield determinations
An Optimal Linear Time Algorithm for Quasi-Monotonic Segmentation
Monotonicity is a simple yet significant qualitative characteristic. We
consider the problem of segmenting a sequence in up to K segments. We want
segments to be as monotonic as possible and to alternate signs. We propose a
quality metric for this problem using the l_inf norm, and we present an optimal
linear time algorithm based on novel formalism. Moreover, given a
precomputation in time O(n log n) consisting of a labeling of all extrema, we
compute any optimal segmentation in constant time. We compare experimentally
its performance to two piecewise linear segmentation heuristics (top-down and
bottom-up). We show that our algorithm is faster and more accurate.
Applications include pattern recognition and qualitative modeling.Comment: This is the extended version of our ICDM'05 paper (arXiv:cs/0702142
- …