1,720,954 research outputs found
Observing the hydrology of China from space - detection of anthropogenic changes in hydrology using spaceborne measurements
No full textIn this study we focus on the use of remotely sensed data, mainly data from the GRACE mission, for the detection of hydrological changes in China. More specifically, the Hai - Huai - Huang basins and the impoundment of the Three Gorges reservoir are studied. Due to noise and the required filtering of the monthly GRACE gravity field solutions there is a limitation on both the magnitude of changes and the spatial scale at which changes occur for these changes to be successfully detected. We investigate if we can detect changes in hydrology in these areas and if it is possible to ascribe detected hydrological changes to anthropogenic water use or water management. The conducted research can be divided into two parts. In the first part we perform a large scale analysis on the different river basins. Precipitation, evapotranspiration and soil moisture are considered for the individual basins and used when analyzing the total water storage variations as computed from GRACE gravity field solutions. Modeled soil moisture variations are found to be unreliable in (part of) the research area. We make assumptions to limit the modeled soil moisture variation and try to compute the groundwater depletion in this area more accurately. In the second part we compute the change in reservoir volume of the Three Gorges reservoir over time using laser altimetry and a Digital Elevation Model. Forward modeling if this signal shows good agreement with results found from monthly GRACE gravity field solutions.Earth and planetary observationsRemote sensingAerospace Engineerin
A Sensitivity Study into Strapdown Airborne Gravimetry
No full textAirborne gravimetry is an important tool for the geodesy and geophysics communities. Able to provide medium to high-resolution measurements over large areas, it is the link between the low-resolution satellite measurements and expensive terrestrial campaigns, especially in remote areas. To explore the potential of airborne gravimetry, the Gravimetry using Airborne Inertial Navigation (GAIN) project was recently established at the faculty of Aerospace Engineering at TU-Delft, and is currently building and testing an in-house strapdown airborne gravimetry system with the objective of providing low-cost, high-accuracy gravity data for use in a wide range of applications in geodesy and geophysics. Within this thesis, the inertial sensors that will be used within the GAIN strapdown IMU are calibrated and modeled with a simulator to predict the accuracy of the airborne system when completed. A sensitivity study of several campaign parameters is done to understand which parts of the hardware and operating conditions are critical to the performance of the system. Of the list of applications for airborne gravity data, natural resource exploration is one of the more demanding in terms of accuracy and resolution, with a requirement of 0.5-2mGal at 2km resolution. This is beyond the range of current strapdown systems, so in addition to assessing the performance of the current strapdown system, additional tests were made to see what would be needed to achieve this higher level of accuracy. The simulation results suggest that the performance of the GAIN strapdown system, under ideal conditions, would be 1.4mGal at 2km resolution. Furthermore, the performance is limited by the accelerometers whose accuracy must improve by a factor of three before the 0.5mGal level can be achieved; however, other options were identified that could also be used to achieve this.Physical and Space GeodesyDepartment of Remote SensingAerospace Engineerin
ICESat full waveform signal analysis for the classification of land cover types over the cryosphere
No full textThe Earth needs attention. That is the bottom line of today’s discussion on the impact of humans on the environment and their contribution to global warming. With the rapid sea level rise and the melting ice caps, it is becoming increasingly important to understand these processes. Mass balance estimates of the cryosphere (e.g. Greenland and Antarctica) are one of the keys to unlocking the secrets of today’s concerns and predicting tomorrow’s problems. The primary objective of this research is to construct an automatic classification algorithm to that will distinguish between the polar land cover types: ice, rock, snow and water. The algorithm is based on full waveform laser altimetry measurements gathered by the Ice, Cloud and Elevation Satellite (ICESat). The results of this research have the potential to play an important role in improving the current methods for computing mass balance estimates and monitoring seasonal changes in land cover type of the cryosphere.GeomaticsAerospace Engineerin
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
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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