1,721,190 research outputs found
Theory of River Meanders
No full textA mathematical model is developed for the calculation of flow field and bed
topography in curved channels with an erodible bed. A small perturbation approach is used
to linearize the governing equations.
The downstream convective acceleration of the secondary flow is shown to give
rise to a phase lag between secondary flow and channel centerline curvature, and also to
suppress the magnitude of the secondary flow. The model further accounts for the
convective transport of primary flow momentum by the secondary flow. This oft-neglected
influence of the secondary flow is shown to be an important cause of the redistribution of
the primary flow velocity.
The governing equations retain the full coupling between the flow field, the bedload
transport, and the bed topography. This coupling is shown to increase significantly the
lateral bed slope in the upstream part of a channel bend, even beyond the value for fully
developed bend flow which is approached in the downstream part of a channel bend. This
coupling is also shown to give rise to resonant behavior for certain combinations of input
variables; the common origin of the two phenomena is explained. The predicted flow field
and bed topography compare very well with both laboratory and field data.
Further, assuming the banks to be erodible, the model is used to predict
wavelengths of river meanders. The results compare favorably with both laboratory and
field data.Legislative Commission of Minnesota ResourcesJohannesson, Helgi; Parker, Gary. (1988). Theory of River Meanders. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/114112
Computer Simulated Migration of Meandering Rivers in Minnesota
No full textIn the present work, a computer model for simulation of the migration of meandering rivers, developed by Beck [1985a], was applied to four rivers in the State of Minnesota. The computer model is based on a theoretical approach developed by Ikeda, Parker, and Sawai [1981]. The major objective was to evaluate the overall performance of the computer model and to estimate the rates of river migration in Minnesota.
By using the model to analysis the past history of the four rivers, it was found that the model is able to reproduce the past river migration but needs considerable calibration. In all the case studies it was necessary to increase the dimensionless friction factor, Cf considerably.
In all the study areas the rivers flow alternately through forested and non-forested areas. It was found that the rivers typically eroded about two times faster thtough non-forested areas than through forested areas. This result is of some interest, especially in agricultural areas. It indicates the importance of having a grove of trees lining the river instead of farming all the way to the river bank.LEGISLATIVE COMMISSION ON MINNESOTA RESOURCES
State of MinnesotaJohannesson, Helgi; Parker, Gary. (1985). Computer Simulated Migration of Meandering Rivers in Minnesota. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/113348
Pork Industry Handbook Feed Additives for Swine (Revised 1978)
No full textThis archival publication may not reflect current scientific knowledge or recommendations. Current information available from the University of Minnesota Extension: https://www.extension.umn.edu.Whiteker, Mack D.; Hays, Virgil W.; Parker, Gary R.. (1978). Pork Industry Handbook Feed Additives for Swine (Revised 1978). Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/205238
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Diagnostic Study of the Siltation Problem at the Wilmarth Power Plant Cooling Water Intake on the Minnesota River
No full textThe Northern States Power Company's Wilmarth Power Plant is
located at the east bank of the Minnesota River just downstream of
Mankato. The plant receives its cooling water from an
adjacent intake on the river. A permanent sand bar is
located on the east bank Of the river just upstream of the intake.
The presence of this bar and its imminent downstream migration threatens
the supply of cooling water from the river for the operation of the plant.Northern States Power CompanyJohannesson, Helgi; Parker, Gary; Garcia, Marcelo; Okabe, Kazunori. (1988). Diagnostic Study of the Siltation Problem at the Wilmarth Power Plant Cooling Water Intake on the Minnesota River. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/114110
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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