118,178 research outputs found
Modeling L- and X-band backscattering of wheat and tests over fields of Pampas
No full textA discrete scattering model and a detailed set of ground measurements are used to simulate the backscattering coefficients of wheat fields during the whole growth cycle. Simulations are carried out at L- and X-band, and at HH, VV, and HV polarizations. Wheat fields are located in Pampas (Argentina), and are characterized by low values of plant density. Simulations show that the backscattering coefficient is driven by variations of soil moisture at L-band, particularly for HH polarization, with low vegetation effects. Conversely, the attenuation of vegetation is dominant in producing variations of backscattering coefficients at X-band, particularly for VV polarization. Simulations are compared against experimental data collected over the same Pampas region, using airborne SARAT SAR at L-band and COSMO-SKYMED at X-band. Assuming a surface height standard deviation in a 0.4-0.7 cm range, the simulations generally agree with experimental data, with an RMSE lower than about 2 dB at L-band and X-band, except a limited number of cases. Discrepancies observed in specific conditions are discussed. Overall, the results indicate that a joint use of L- and X-band has a good potential to monitor both soil moisture and vegetation growth
Modelling L band backscattering of wheat in Argentinean Pampas and its application to soil moisture retrieval
No full textIn this paper a data base of L band backscattering simulations, based on the application of a discrete scattering model and detailed ground truth collected over Argentinean wheat fields, is tested. The simulations are directly compared against backscattering measurements collected over single fields. Then the scattering model is used to tune a semi empirical and manageable model function. Finally this function, jointly with a multi-temporal algorithm, is used for soil moisture retrieval and results are tested against an independent set of measurements. The site used for training and validation is located in the Pampas region, which will be continuously monitored in the framework of the SAOCOM (SAtélite Argentino de Observación COn Microondas) programme. In general, both the direct model and the retrieval algorithm produce consistent results. However, variation in the azimuth angle of observation produces appreciable effects, and some discrepancies are observed for radar observations collected just after a rainfall. These issues deserve further investigation with a larger amount of experimental data
The effect of temperature and artificial diets on the growth rate of juvenile Haliotis turberculata
No full textSAR signature modeling of the Pampas region main crops
No full textOn October 7th, 2018 the SAOCOM (Satélite Argentino de Observación Con Microondas) 1A was launched, carrying an L band, full-polarimetric SAR on board. The SAOCOM 1B, an identical satellite allowing a revisit time of 8 days, is planned to be launched on March 30th, 2020. Both SAOCOM satellites belong to CONAE (National Space Activities Commission of Argentina) and form part of the ItalianArgentine System of Satellites for Emergency Management (SIASGE) constellation, also including four X band (~9.6 GHz) SAR-equipped COSMO-SkyMed satellites from the Italian Space Agency (ASI). One of the main objectives of the SAOCOM project is related to land and agricultural applications. Extracting land information from radar signatures is a complex issue and the present thesis shows part of the trip we are doing to develop crop applications. This thesis is focused on backscattering simulations over some of the most important crop fields in Argentina, that is, soybeans, maize and wheat. The dedicated area to each crop is 17, 7 and 6 million hectares correspondingly. Simulations are carried out at L- and X-band, and at HH, VV, and HV polarizations, and are based on the application of a discrete scattering model and detailed ground truth collected over the Argentinean Pampas region, used to simulate the backscattering coefficients of crop fields during the entire growth cycle. The wheat fields simulations show that the backscattering coefficient is driven by variations of soil moisture at L-band, particularly at HH polarization, with low vegetation effects. Conversely, the attenuation of vegetation is dominant in producing variations of backscattering coefficients at X-band, particularly at VV polarization. Simulations are compared against experimental data collected over the same Pampas region, using airborne SARAT SAR at L-band and COSMO-SKYMED at X-band. Assuming a surface height standard deviation in a 0.4-0.7 cm range, the simulations generally agree with experimental data, with an RMSE of about 2 dB at L-band and X-band. Discrepancies observed in specific conditions are discussed in the thesis. Overall, the results indicate that a joint use of L- and X-bands has good potential to monitor both soil moisture and vegetation growth. We carried out a test using measurements over US maize fields collected by airborne PALS (Passive and Active L and S band) sensor during the SMEX-2002 campaign, finding that simulations (from Argentinean crop inputs) produce a general agreement on the trend of backscattering coefficient vs. vegetation water content. However, experimental data show some outliers, particularly at HH polarization, which are not explained by the model and the available ground measurements. A completely developed soybeans model was tested against ALOS-2 (Advanced Land Observing Satellite-2; SAR mission) signatures collected over Argentinean soybean fields during 2017 on the site of Monte Buey, located in Pampas. A general agreement is observed also in this case, with some underestimation which can be due to the appearance of the sheath, not yet considered by the model
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
Square Dancing with the Stars to Enhance Dynamic Hirschman Linkages?
No full textIn this Presidential Address, the author takes the reader on a reconnaissance of his life and time as a regional scientist. He points out scenery he found scintillating along the way, hoping that some may pick up the banner and chew on a few of the ideas for a while. He suggests a revisit to Albert O. Hirschman’s notion of key sectors and more empirical analysis related to Marcus Berliant’s and Masahisa Fujita’s notion of knowledge creation and transfer.Presidential Address, San Antonio, Texas, March 29, 2014 (53rd Meetings of the Southern Regional Science Association
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe 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
Letter from unknown writer to Jesse L. Boyce
No full textLetter to Jesse L. Boyce from unknown author (possibly Jack) about the investigation into the powder magazine located in the Grand Canyon. Some personal news is included in the letter such as the writer's marriage to the daughter of C.A. Taylor, former Supervisor of Cochise County
Dispelling the Myths Behind First-author Citation Counts
No full textWe 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
Moisture dependence on mechanical properties of pine nuts from Pinus pinea L
No full text[EN] Mechanical properties of pine nut shell are very important in the cracking process. Before industrial cracking shell moisture is adjusted by water soaking in order to avoid the breaking up of the nuts. In this work the moisture dependence of the mechanical properties of pine nut shells were studied in order to improve the industrial cracking process.
Relationship between nut size and moisture content was studied and no significant differences were found for shell dimensions at four different moisture levels, 9.79%, 16.71%, 20.98% and 25.05% (dry basis). Compression tests were carried out on pine nuts at nine different moisture contents between 1.38% and 25.48% (db) and their main mechanical parameters were evaluated. Nut shell has a characteristic behavior under compression loading. Rupture force, rupture deformation, elasticity and rupture energy of shell were found to be moisture dependent. Values of rupture force decreased linearly from 0.24 to 0.49 kN, rupture deformation and rupture energy increased initially with moisture until stabilization at asymptotic values of about 1.8 mm and 0.22 J, respectively. Elasticity index of the shell decreased linearly with moisture from 1 to 0.4 kN/mm. (C) 2011 Elsevier Ltd. All rights reserved.Cárcel, LM.; Bon Corbín, J.; Acuna, L.; Nevares, I.; Del Álamo Sanza, M.; Crespo, R. (2012). Moisture dependence on mechanical properties of pine nuts from Pinus pinea L. Journal of Food Engineering. 110(2):294-297. doi:10.1016/j.foodeng.2011.04.018S294297110
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