1,720,957 research outputs found
The contribution of W-band radar monitoring for understanding of runoff and soil erosion response at field scale
Full text linkVegetation cover has a great influence on hydrological response at field scale, and, consequently, on runoff and soil erosion processes. The maintenance of bare soil in vineyard inter-rows with tillage, as well as the tractor traffic, are known to expose the soil to compaction, reduction of soil water holding capacity and increase of runoff and erosion. The use of grass cover is one of the most common and effective practices in order to reduce such threats. Rain-driven runoff (RO) and soil loss (SL) at sites with different cover have been investigated over last decades. It has been found that RO and SL often correlate with rain properties. This correlation, however, is highly variable among different sites and also for different time periods. In many studies rain is represented only by a few parameters such as e.g. maximum intensity and total precipitation. Size of rain drops is rarely analysed, although it is important for an accurate estimation of kinetic energy of rain. Polarimetric millimetre-wavelength radars are one of the instruments capable of drop size measurements. In contrast to in-situ rain sensors, such radars have much larger sampling area and can estimate range profiles of drop size distributions with high spatial and temporal resolution. The objective of this work is to relate runoff and soil erosion to rain properties based on traditional monitoring techniques complemented by observations from a radar. With this aim, a site in the Alto Monferrato vine-growing area (Piedmont, NW Italy) was equipped with a 94-GHz radar in June 2023. The site has two vineyard-field-scale plots with inter-rows managed with conventional tillage (CT) and grass cover (GC), respectively. The radar is located about 100 m from the plots. The radar elevation was set to 30° so that the radar samples rain above the plots. During the summer and autumn seasons of 2023, 26 rain and 13 runoff events were observed. The preliminary results of the conventional analysis show that in this period runoff is directly related to erosivity index (EI30) both in CT and GC plots, and, only in GC treatment to maximum rainfall intensity over 10 minutes and antecedent rainfall in previous 7 days. Maximum rainfall intensity over 30 and 60 minutes, on the contrary, has a negative direct proportion with runoff. Soil erosion for both treatments was also directly related also with maximum rainfall intensity over 10 minutes and antecedent rainfall in previous 7 days and, in addition has a negative proportion with rainfall energy. It should be noted the relevant role played by rainfall intensity over short time interval and the antecedent rainfall, resulting in increased soil moisture. Relationships are different from those obtained in the same site in a previous study, reflecting the peculiarity of summer 2023, characterized by few rainfall events occurred on very dry soil. Information obtained from W-Band radar monitoring allows to investigate relationships in a deeper way among rainfall characteristics and generation of runoff and soil erosion
Assessment of Ground-Based Microwave Radiometer Calibration to Enable Investigation of Gas Absorption Models
No full textGround-based microwave radiometers are becoming more and more common for remotely sensing the atmospheric temperature and humidity profile, as well as path integrated cloud liquid water content. Several studies have been published, which compare radiosonde profiles with temperature profiles derived from microwave radiometer measurements and find biases of up to 1 K. The retrieved temperature profile is based on radiometric measurements and radiative transfer calculations. Once the accuracy of radiometer measurements is known, these can be used to validate existing gas absorption models. As the absolute accuracy of microwave radiometer measurements is determined by the quality of the calibration, this work investigates the uncertainty of two calibration techniques, which are commonly used with microwave radiometers. Namely, these are the liquid nitrogen calibration and the tipping curve calibration (Han and Westwater, 2000). Both methods are known to have open issues concerning systematic offsets and calibration repeatability.
In this regard, this work focuses on the error assessment for the absolute calibration of the network suitable microwave radiometer HATPRO-G2 (Humidity And Temperature PROfiler - Generation 2), which makes up a significant part of the worldwide available systems (Rose et al., 2005). In order to capture dry high altitude conditions on the one side and mid-latitude, close to sea level conditions on the other side, the analysis is based on two deployments. Between August and October 2009, HATPRO-G2 was part of the Radiative Heating of Underexplored Bands Campaign - Part 2 (RHUBC-II) in Northern Chile (5320 m above mean sea level) conducted within the Atmospheric Radiation Measurement (ARM) program. Since 2010, it is part of the JOYCE (Jülich ObservatorY for Cloud Evolution) site located in Germany 92 m above mean sea level. For each of the deployments, a detailed error propagation for both techniques is performed.
The uncertainty range of brightness temperature Tb measurements based on a single liquid nitrogen calibration is mainly caused by a reflective component from the liquid nitrogen surface of the cold calibration target. The overall calibration uncertainty is assessed for typical Tb values measured at each deployment. For RHUBC-II, the maximum uncertainty of has been determined to +-1.6 K in the K-band and to +-1.0 K in the V-band. For JOYCE, the maximum uncertainty is assessed to be +-1.5 K in the K-band and +-0.6 K in the V-band. When a standing wave phenomena at the cold calibration point is eliminated by averaging several calibrations, the uncertainty in the K-band can be reduced to +-0.8 K for both deployments. In the V-band, the uncertainties are reduced to values less or equal +-0.7 K for both deployments. Furthermore, the analyses of the liquid nitrogen calibration has revealed, that the pressure dependent boiling point correction for liquid nitrogen, originally used by HATPRO-G2, is only exact for standard pressure conditions. Therefore, the boiling point correction has been modified and is now valid for all altitudes. At the low pressure conditions of RHUBC-II (530 hPa), the improved boiling point correction shifts the cold target temperature compared to the previously used formulation by more than 1 K.
HATPRO-G2 has seven channels in the K-band and seven channels in the V-band. At standard pressure conditions, only the K-band channels are transparent enough to be calibrated by the tipping curve calibration. However, at 530 hPa, the technique can be applied to two low opacity channels in the V-band as well. This offers the unique opportunity of an independent validation of the liquid nitrogen calibration in the V-band. The analysis shows, that the uncertainty in the tipping curve calibration is mainly due to atmospheric inhomogeneities. For RHUBC-II, the total uncertainty is assessed to be +-0.1 K to +-0.2 K in the K-band and +-0.6 K and +-0.7 K for the two V-band channels at 51 GHZ and 52 GHz. For the low altitude deployment at JOYCE, the total uncertainties for K-band channels are +-0.2 K to +-0.6 K.
Finally, the well-characterized radiometer measurements are used to investigate current absorption models. The profiles of temperature, humidity, and pressure from 62 clear sky radiosondes are used for Tb simulations at zenith and compared to HATPRO-G2 measurements. Biases, outside the uncertainty range of the calibration can be ascribed to errors within the gas absorption coefficients. It is found that the results of the Atmospheric Model (AM)(Paine, 2012), which uses the most recent oxygen absorption parameters (Tretyakov et al., 2005, Makarov et al., 2011), are closest to RHUBC-II measurements
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
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
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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