12,806 research outputs found
Weather and Climate Summary and Forecast: January 2020 Report
This report provides a summary of the weather and climate forecast for January 2020. It includes forecast information specific to the Pacific Northwest and the western United States, as well as forecast information for other portions of the United States and abroad
Vintage Report 2019: North Willamette Valley
This report describes the impacts of climate and phenology on vintage for the North Willamette Valley in Oregon in 2019. A relatively mild early winter in 2018 was followed by a cold and wet second half of winter in 2019 and then a wet, but warm, spring. The growing season saw a few mild frosts during late April, but started off warmer than average, moderating through mid-vintage with fewer than average heat spikes. Near-record precipitation amounts during late June and early July brought increased disease pressure to the region. The vintage will be remembered for the early rains in September and rapid cool-down into October, which challenged harvesting decisions. Degree-day totals for 2019 ended up similar to 2012 and 2018, marked by the lowest heat accumulation experienced in September and October since 2007. Phenological timing and interval lengths were similar to observations in 2018 averaging April 16th for bud break, June 8th for bloom, August 14th for véraison, and September 27th for harvest. The cool vintage came largely from substantially lower maximum temperatures while minimum temperatures were near average to slightly above average. This was largely the result of higher humidity levels, which also brought greater disease pressure
Weather and Climate Summary and Forecast: November 2019 Report
This report provides a summary of the weather and climate forecast for November 2019. It includes forecast information specific to the Pacific Northwest and the western United States, as well as forecast information for other portions of the United States and abroad
Weather and Climate Summary and Forecast: October 2019 Report
This report provides a summary of the weather and climate forecast for October 2019. It includes forecast information specific to the Pacific Northwest and the western United States, as well as forecast information for other portions of the United States and abroad
Parameterized Algorithms for Load Coloring Problem
One way to state the Load Coloring Problem (LCP) is as follows. Let
be graph and let be a 2-coloring. An
edge is called red (blue) if both end-vertices of are red (blue).
For a 2-coloring , let and be the number of red and blue edges
and let . Let be the maximum of
over all 2-colorings.
We introduce the parameterized problem -LCP of deciding whether , where is the parameter. We prove that this problem admits a kernel with
at most . Ahuja et al. (2007) proved that one can find an optimal
2-coloring on trees in polynomial time. We generalize this by showing that an
optimal 2-coloring on graphs with tree decomposition of width can be found
in time . We also show that either is a Yes-instance of -LCP
or the treewidth of is at most . Thus, -LCP can be solved in time
$O^*(4^k).
Kernels for Below-Upper-Bound Parameterizations of the Hitting Set and Directed Dominating Set Problems
In the {\sc Hitting Set} problem, we are given a collection of
subsets of a ground set and an integer , and asked whether has a
-element subset that intersects each set in . We consider two
parameterizations of {\sc Hitting Set} below tight upper bounds: and
. In both cases is the parameter. We prove that the first
parameterization is fixed-parameter tractable, but has no polynomial kernel
unless coNPNP/poly. The second parameterization is W[1]-complete,
but the introduction of an additional parameter, the degeneracy of the
hypergraph , makes the problem not only fixed-parameter
tractable, but also one with a linear kernel. Here the degeneracy of
is the minimum integer such that for each the
hypergraph with vertex set and edge set containing all edges of
without vertices in , has a vertex of degree at most
In {\sc Nonblocker} ({\sc Directed Nonblocker}), we are given an undirected
graph (a directed graph) on vertices and an integer , and asked
whether has a set of vertices such that for each vertex there is an edge (arc) from a vertex in to . {\sc Nonblocker} can be
viewed as a special case of {\sc Directed Nonblocker} (replace an undirected
graph by a symmetric digraph). Dehne et al. (Proc. SOFSEM 2006) proved that
{\sc Nonblocker} has a linear-order kernel. We obtain a linear-order kernel for
{\sc Directed Nonblocker}
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