5,668 research outputs found
The Effects of Tidal Forcing on Nutrient Fluxes in the Tidal, Freshwater James River Estuary, VA
A 12-month study (January to December 2015) focused on the effects of tidal forcing on nutrient fluxes in the tidal, freshwater segment of the James River Estuary (JRE). Discrete sampling of nutrient chemistry and continuous monitoring of tidal discharge were used to determine the volume and timing of the tides, and differences in nutrient concentrations between incoming and outgoing tides. The goal of this study was to improve understanding of tidal influence on nutrient fluxes and their role in nutrient transport to the lower estuary. Results suggested that differences in nutrient concentrations between incoming and outgoing tides were small throughout the year. This finding suggests that nutrient fluxes at the study site, near the tidal fresh-oligohaline boundary of the James, are largely determined by tidal volume owing to weak concentrations gradients. Changes in water quality during seaward and landward tidal excursions into deeper versus shallower segments were analyzed to infer biogeochemical processes. Differences in oxygen production and nitrate utilization suggest greater autotrophy during landward excursions, consistent with more favorable light conditions. This work was conducted as a collaborative effort between Virginia Commonwealth University, the USGS, Randolph-Macon College, and Washington and Lee University participating in the “Mountains to the Sea” project
Kolmogorov widths under holomorphic mappings
If is a bounded linear operator mapping the Banach space into the
Banach space and is a compact set in , then the Kolmogorov widths of
the image do not exceed those of multiplied by the norm of . We
extend this result from linear maps to holomorphic mappings from to
in the following sense: when the widths of are for some
r\textgreater{}1, then those of are for any s \textless{}
r-1, We then use these results to prove various theorems about Kolmogorov
widths of manifolds consisting of solutions to certain parametrized PDEs.
Results of this type are important in the numerical analysis of reduced bases
and other reduced modeling methods, since the best possible performance of such
methods is governed by the rate of decay of the Kolmogorov widths of the
solution manifold
Approximation of high-dimensional parametric PDEs
Parametrized families of PDEs arise in various contexts such as inverse
problems, control and optimization, risk assessment, and uncertainty
quantification. In most of these applications, the number of parameters is
large or perhaps even infinite. Thus, the development of numerical methods for
these parametric problems is faced with the possible curse of dimensionality.
This article is directed at (i) identifying and understanding which properties
of parametric equations allow one to avoid this curse and (ii) developing and
analyzing effective numerical methodd which fully exploit these properties and,
in turn, are immune to the growth in dimensionality. The first part of this
article studies the smoothness and approximability of the solution map, that
is, the map where is the parameter value and is the
corresponding solution to the PDE. It is shown that for many relevant
parametric PDEs, the parametric smoothness of this map is typically holomorphic
and also highly anisotropic in that the relevant parameters are of widely
varying importance in describing the solution. These two properties are then
exploited to establish convergence rates of -term approximations to the
solution map for which each term is separable in the parametric and physical
variables. These results reveal that, at least on a theoretical level, the
solution map can be well approximated by discretizations of moderate
complexity, thereby showing how the curse of dimensionality is broken. This
theoretical analysis is carried out through concepts of approximation theory
such as best -term approximation, sparsity, and -widths. These notions
determine a priori the best possible performance of numerical methods and thus
serve as a benchmark for concrete algorithms. The second part of this article
turns to the development of numerical algorithms based on the theoretically
established sparse separable approximations. The numerical methods studied fall
into two general categories. The first uses polynomial expansions in terms of
the parameters to approximate the solution map. The second one searches for
suitable low dimensional spaces for simultaneously approximating all members of
the parametric family. The numerical implementation of these approaches is
carried out through adaptive and greedy algorithms. An a priori analysis of the
performance of these algorithms establishes how well they meet the theoretical
benchmarks
\u3cem\u3eLaunching through the Surf\u3c/em\u3e Traveling Exhibit Panel 15: Yamhill County Connections
McMinnville and other Yamhill County cities have had a close association with Pacific City and the dory fleet since the late 1800s. Panel 15 is the first of two panels that chronicle the issues and the people who have forged those ties. The panel features vintage photographs from the collections of dory fishers interviewed for the project.https://digitalcommons.linfield.edu/dory_exhibit/1014/thumbnail.jp
\u3cem\u3eLaunching through the Surf\u3c/em\u3e Traveling Exhibit Panel 01: Title
Panel one serves as the title panel of the traveling exhibit. It was adapted from the cover designed by Candido Salinas for the Fall 2012 issue of the Linfield Magazine. The panel features a vintage photograph from the Coon Family Collection depicting double-enders launching from the beach in 1957.https://digitalcommons.linfield.edu/dory_exhibit/1000/thumbnail.jp
\u3cem\u3eLaunching through the Surf\u3c/em\u3e Traveling Exhibit Panel 13: Blessing of the Fleet
Like many fishing communities, the Pacific City dory community honors its fleet, asks for bountiful and safe fishing for the coming season, and remembers those who have died during the year at the annual Blessing of the Fleet. The ceremony is held on the beach the first Saturday in June. In a similar vein, the community celebrates the dories and honors those who made significant contributions to the fleet and the community during the Memorial Wall Ceremony. This observance normally takes place during Dory Days. Panel 13 describes both of these events.https://digitalcommons.linfield.edu/dory_exhibit/1012/thumbnail.jp
\u3cem\u3eLaunching through the Surf\u3c/em\u3e Traveling Exhibit Panel 02: Historical Highlights
The first of three panels in the exhibit that provide general historical highlights about the Dory Fleet, panel two features a timeline of events from 1855 to 1935. It incorporates a section from the Oregon House Calendar of 1927, chronicling the introduction and passage of House Bill 282. This legislation closed the Nestucca River to commercial fishing. The panel also includes an excerpt from the 1927 version of the Oregon Voters’ Pamphlet that describes an initiative to overturn the legislative action.https://digitalcommons.linfield.edu/dory_exhibit/1001/thumbnail.jp
\u3cem\u3eLaunching through the Surf\u3c/em\u3e Traveling Exhibit Panel 09: Building a Dory
Panel 9 documents the process of building a dory. During the winter and spring of 2012, project collaborator Tyrone Marshall photographed Pacific City dory builder Terry Learned as he crafted dory number 82, the Rehab.https://digitalcommons.linfield.edu/dory_exhibit/1008/thumbnail.jp
\u3cem\u3eLaunching through the Surf\u3c/em\u3e Traveling Exhibit Panel 14: The Memorial Wall
Incorporating drawings and photographs from the Tom Donohue Collection, panel 14 documents the process of building the Memorial Wall at Cape Kiwanda, as well as its dedication in 2009.https://digitalcommons.linfield.edu/dory_exhibit/1013/thumbnail.jp
\u3cem\u3eLaunching through the Surf\u3c/em\u3e Traveling Exhibit Panel 18: The Project - The Play
Panel 18 depicts the development of the production of Kickin’ Sand and Tellin’ Lies, a play based on the oral histories collected during the project. The play was performed in November 2012 at the Marshall Theatre on the Linfield College campus in McMinnville and at the Kiawanda Community Center in Pacific City. It is the second of three exhibit panels that chronicle the Launching through the Surf project.https://digitalcommons.linfield.edu/dory_exhibit/1017/thumbnail.jp
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