1,721,062 research outputs found
Assessment of pasture production in the Italian Alps using spectrometric and remote sensing information
No full textThree years of summer field studies (2002-2004) were conducted at two sites in the Central Italian Alps. Field spectroradiometer data were acquired on different vegetation typologies where current above ground biomass was measured with traditional agronomic methods. Radiometric measurements were synthesised into a set of spectral vegetation indices. Log-transformed regression analysis between fresh biomass and spectral vegetation indices indicated that soil adjusted vegetation indices (SAVI, MSAVI and OSAVI) show a better correlation (r 2 >0.60) than more commonly employed indices as SR and NDVI (r 2 <0.50). Cross validation procedure showed that a regressive model based on MSAVI index was the most predictive. Analysis of covariance revealed that data from different years and vegetation types significantly influenced the relation, however no improvement in the regressive model was found when data were used separately. After a suitable calibration procedure, a fresh biomass map of the study area was obtained using Landsat-7 imagery. Results showed that the integrated use of field spectral measurements and satellite
derived information can provide a valuable support to the assessment of pasturebiomass production in alpine environment
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
Land-use and land-cover change detection in a semi-arid area of Niger using multi-temporal analysis of Landsat images
No full textRecent studies using low-resolution satellite time series show that the Sahelian belt of West Africa is witnessing an increase in vegetation cover/biomass, called re-greening. However, detailed information on local processing and changes is rare or lacking. A multi-temporal set of Landsat images was used to produce land-cover maps for the years 2000 and 2007 in a semi-arid region of Niger, where an anomalous vegetation trend was previously detected. Several supervised classification approaches were tested: spectral classification of single Landsat data, temporal classification of normalized difference vegetation index time series from Landsat images, and two-step classification integrating both these approaches. The accuracy of the land-cover maps obtained ranges between 80% and 90% overall for the two-step classification approach. Comparison of the maps between the two years indicates a stable semi-arid region, where some change in hot spots exists despite a generally constant level of rainfall in the area during this period. In particular, the Dallol Bosso fossil valley highlights an increase in cultivated land, while a decrease in herbaceous vegetation was observed outside the valley where rangeland is the predominant natural landscape
Estimation of parameters describing morpho-physiological features of MEditerranean rice varieties for modelling purposes
No full textThis paper illustrates the estimation of parameters describing some morphological and physiological characteristics of Japonica-type and Indica-type rice varieties to be used in crop modelling simulation. Seasonal variability of the Specific Leaf Area (SLA; m2 kg-1) parameter was calculated from biomass and LAI measurements. Coefficient of light extinction (k; -) was estimated by transmittance measurements recorded by LAI2000 in 2004 experiment. Radiation use efficiency (RUE; g MJ-1) was derived by regressive analysis between different above ground biomass measurements and corresponding cumulative APAR using field experimental data set acquired in different years (2004, 2003, 2002, 1990).
Results show that development stage determines more variability in SLA than cultivar typology. K parameter varies during the different plant developing stages in agreement with other published data; however, no significative difference is evident among the varieties, representative of different rice-group, when a mean seasonal value (K=0.53; -) is derived. The analysis highlighted a sensible difference in RUE values between traditional tall Japonica variety (1.83, g MJ-1) and new semi-dwarf Indica variety (3.14, g MJ-1). A method to considered possible thermal limitation that decrease RUE values derived by field experiment is proposed to obtain reasonable figure of maximum potential RUE to be used in crop models. Applying this procedure a maximum RUE for Japonica medium late and Indica Early varieties can be set respectively to 2.69 and 3.25 g MJ-1
Operational Monitoring of Daily Crop Water Requirements at the Regional Scale with Time Series of Satellite Data
No full textThis work presents a simple, cost-effective, and operational approach to monitor crop water requirements at the regional scale for water management and monitoring purposes. The recommended Food and Agricultural Organization of the United Nations methodology (FAO-56) calculates crop evapotranspiration using crop-specific coefficients (Kc), which vary according to the crop type, health, and phenological stage. This approach, though widely applied for irrigation planning, cannot always match the appropriate crop coefficient with the actual crop phenological stage and health condition, especially in anomalous situations. Previous research demonstrated that crop coefficients and spectral vegetation indexes are correlated. Recent studies have used this relationship with high-resolution satellite data from different sensors to provide information to irrigation advisory services. However, high-resolution data are not feasible for an operational and routine monitoring of water consumption and needs. This paper tests the usefulness of time series of coarse resolution satellite data such as those collected by the moderate-resolution imaging spectroradiometer (MODIS) sensor, to monitor crop coefficients temporal and spatial variability and therefore crop water needs at the regional scale taking advantage of the peculiar characteristics offered by MODIS in terms of high temporal resolution and preprocessed products availability. The outlined methodology takes into account the actual growing stage of the crops and nearly real-time vegetation variations, overcoming some limitations of the traditional FAO approach while preserving the maximum operability. The analysis was carried out in the South Milan agricultural area on data referring to 2003 and 2004. The results agreed with those of other studies and proved to be able to account for the anomalous conditions of the summer in 2003. These results were then compared with those obtained using the traditional FAO crop coefficient curves built with data collected during field campaigns in the same years in rice fields. Constraints, limitations, and possible uses are discussed
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