1,720,972 research outputs found
Debris thickness of glaciers in the Everest area (Nepal Himalaya) derived from satellite imagery using a nonlinear energy balance model
Get PDFDebris thickness is an important characteristic of debris-covered glaciers
in the Everest region of the Himalayas. The debris thickness controls the
melt rates of the glaciers, which has large implications for hydrologic
models, the glaciers' response to climate change, and the development of
glacial lakes. Despite its importance, there is little knowledge of how the
debris thickness varies over these glaciers. This paper uses an energy
balance model in conjunction with Landsat7 Enhanced Thematic Mapper Plus (ETM+) satellite imagery to
derive thermal resistances, which are the debris thickness divided by the
thermal conductivity. Model results are reported in terms of debris
thickness using an effective thermal conductivity derived from field data.
The developed model accounts for the nonlinear temperature gradient in the
debris cover to derive reasonable debris thicknesses. Fieldwork performed on
Imja–Lhotse Shar Glacier in September 2013 was used to compare to the
modeled debris thicknesses. Results indicate that accounting for the
nonlinear temperature gradient is crucial. Furthermore, correcting the
incoming shortwave radiation term for the effects of topography and
resampling to the resolution of the thermal band's pixel is imperative to
deriving reasonable debris thicknesses. Since the topographic correction is
important, the model will improve with the quality of the digital elevation model (DEM). The main
limitation of this work is the poor resolution (60 m) of the satellite's
thermal band. The derived debris thicknesses are reasonable at this
resolution, but trends related to slope and aspect are unable to be modeled
on a finer scale. Nonetheless, the study finds this model derives reasonable
debris thicknesses on this scale and was applied to other debris-covered
glaciers in the Everest region
Debris-covered glacier energy balance model for Imja–Lhotse Shar Glacier in the Everest region of Nepal
Get PDFDebris thickness plays an important role in regulating ablation rates on debris-covered glaciers as well as controlling the likely size and location of supraglacial lakes. Despite its importance, lack of knowledge about debris properties and associated energy fluxes prevents the robust inclusion of the effects of a debris layer into most glacier surface energy balance models. This study combines fieldwork with a debris-covered glacier energy balance model to estimate debris temperatures and ablation rates on Imja-Lhotse Shar glacier located in the Everest region of Nepal. The debris properties that significantly influence the energy balance model are the thermal conductivity, albedo, and surface roughness. Fieldwork was conducted to measure thermal conductivity and a method was developed using Structure from Motion to estimate surface roughness. Debris temperatures measured during the 2014 melt season were used to calibrate and validate a debris-covered glacier energy balance model by optimizing the albedo, thermal conductivity, and surface roughness at 10 debris-covered sites. Furthermore, three methods for estimating the latent heat flux were investigated. Model calibration and validation found the three methods had similar performance; however, comparison of modeled and measured ablation rates revealed that assuming the latent heat flux is zero may overestimate ablation. Results also suggest that where debris moisture is unknown, measurements of the relative humidity or precipitation may be used to estimate wet debris periods, i.e., when the latent heat flux is non-zero. The effect of temporal resolution on the model was also assessed and results showed that both 6-hour data and daily average data slightly underestimate debris temperatures and ablation rates, thus these should only be used to estimate rough ablation rates when no other data are available
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Changes in Imja Tsho in the Mount Everest region of Nepal
Get PDFImja Tsho, located in the Sagarmatha (Everest) National Park of Nepal, is one
of the most studied and rapidly growing lakes in the Himalayan range.
Compared with previous studies, the results of our sonar bathymetric survey
conducted in September of 2012 suggest that its maximum depth has increased
from 90.5 to 116.3 ± 5.2 m since 2002, and that its estimated volume
has grown from 35.8 ± 0.7 to 61.7 ± 3.7 million m3. Most of
the expansion of the lake in recent years has taken place in the glacier
terminus–lake interface on the eastern end of the lake, with the glacier
receding at about 52 m yr−1 and the lake expanding in area by
0.04 km2 yr−1. A ground penetrating radar survey of the
Imja–Lhotse Shar glacier just behind the glacier terminus shows that the ice
is over 200 m thick in the center of the glacier. The volume of water that
could be released from the lake in the event of a breach in the damming
moraine on the western end of the lake has increased to 34.1 ± 1.08
million m3 from the 21 million m3 estimated in 2002
Variations on the Author
Get PDF“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
Get PDFWe 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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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