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Start Over Descriptor "Classification results" Publisher elsevier b.v.
3 results on '"Classification results"'

1. Improving hyperspectral image segmentation by applying inverse noise weighting and outlier removal for optimal scale selection

Author

Dao, P. D., Mantripragada, K., He, Y., Qureshi, F. Z., Dao, P. D., Mantripragada, K., He, Y., and Qureshi, F. Z.

Abstract

Optimal scale selection for image segmentation is an essential component of the Object-Based Image Analysis (OBIA) and interpretation. An optimal segmentation scale is a scale at which image objects, overall, best represent real-world ground objects and features across the entire image. At this scale, the intra-object variance is ideally lowest and the inter-object spatial autocorrelation is ideally highest, and a change in the scale could cause an abrupt change in these measures. Unsupervised parameter optimization methods typically use global measures of spatial and spectral properties calculated from all image objects in all bands as the target criteria to determine the optimal segmentation scale. However, no studies consider the effect of noise in image spectral bands on the segmentation assessment and scale selection. Furthermore, these global measures could be affected by outliers or extreme values from a small number of objects. These issues may lead to incorrect assessment and selection of optimal scales and cause the uncertainties in subsequent segmentation and classification results. These issues become more pronounced when segmenting hyperspectral data with large spectral variability across the spectrum. In this study, we propose an enhanced method that 1) incorporates the band's inverse noise weighting in the segmentation and 2) detects and removes outliers before determining segmentation scale parameters. The proposed method is evaluated on three well-established segmentation approaches – k-means, mean-shift, and watershed. The generated segments are validated by comparing them with reference polygons using normalized over-segmentation (OS), under-segmentation (US), and the Euclidean Distance (ED) indices. The results demonstrate that this proposed scale selection method produces more accurate and reliable segmentation results. The approach can be applied to other segmentation selection criteria and are useful for automatic multi-parameter tuning and op

Published
2021
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2. Assessment of spray drift potential reduction for hollow-cone nozzles: Part 1. Classification using indirect methods

Author

Xavier Torrent, Joan R. Rosell-Polo, Jean-Paul Douzals, Cyril Tinet, Eduard Gregorio, Santiago Planas, Universitat de Lleida, Information – Technologies – Analyse Environnementale – Procédés Agricoles (UMR ITAP), Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Institut national d’études supérieures agronomiques de Montpellier (Montpellier SupAgro), and Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)

Subjects
DRIFT REDUCTION, Drift, Environmental Engineering, DROPLET SIZES, 010504 meteorology & atmospheric sciences, DROPLET SIZE, Analyser, Nozzle, Drift potential, 010501 environmental sciences, 01 natural sciences, Reduction (complexity), Spray, Nozzle classification, CLASSIFICATION RESULTS, DRIFT DEPOSITION, Environmental Chemistry, Waste Management and Disposal, 0105 earth and related environmental sciences, Wind tunnel, Droplet size, INDIRECT METHODS, Pollution, POLLUTION SOURCES, Phase doppler, Pesticide, 13. Climate action, [SDE]Environmental Sciences, Spray drift, Particle, Environmental science, DRIFT POTENTIAL, SPRAY NOZZLES, WIND TUNNELS, NOZZLE CLASSIFICATION, Marine engineering
Abstract

Spray drift is one of the main pollution sources identified when pesticides are sprayed on crops. In this work, in order to simplify the evaluation of hollow-cone nozzles according to their drift potential reduction, several models commonly used were tested by three indirect methods: phase Doppler particle analyser (PDPA) and two different wind tunnels. The main aim of this study is then to classify for the first time these hollow-cone nozzle models all of them used in tree crop spraying (3D crops). A comparison between these indirect methods to assess their suitability and to provide guidelines for a spray drift classification of hollow-cone nozzles was carried out. The results show that, in general terms, all methods allow hollow-cone nozzle classifications according to their drift potential reduction (DPR) with a similar trend. Among all the parameters determined with the PDPA, the V100 parameter performed best in differentiating the tested nozzles among drift reduction classes. In the wind tunnel, similar values were obtained for both sedimenting and airborne drift depositions. The V100 parameter displayed a high correlation (up to R2 = 0.948) with the drift potential tested with the wind tunnel. It is concluded that in general, the evaluated indirect methods provide equivalent classification results. Additional studies with a greater variety of nozzle types are required to achieve a proposal of harmonized methodology for testing hollow-cone nozzles. This work was partly funded by the Secretaria d'Universitats i Recerca del Departament d'Empresa i Coneixement de la Generalitat de Catalunya, the Spanish Ministry of Economy and Competitiveness and the European Regional Development Fund (ERDF) under Grants 2017 SGR 646, AGL2007-66093-C04-03, AGL2010-22304-04-C03-03, and AGL2013-48297-C2-2-R. The authors also wish to thank Mr. Antonio Checa (Randex Iberica, S.L.) for giving us free Albuz nozzles for the spray tests. Universitat de Lleida is also thanked for Mr. X. Torrent's pre-doctoral fellowship.

Published
2019
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3. On the mean value property of fractional harmonic functions.

Author

Bucur, Claudia, Dipierro, Serena, and Valdinoci, Enrico

Subjects
*HARMONIC functions, *VALUATION, *LEBESGUE measure, *SET functions, *MEAN value theorems, *NORMALIZED measures
Abstract

As is well known, harmonic functions satisfy the mean value property, i.e. the average of such a function over a ball is equal to its value at the center. This fact naturally raises the question on whether this is a feature characterizing only balls, namely, is a set, for which all harmonic functions satisfy the mean value property, necessarily a ball? This question was investigated by several authors, including Bernard Epstein (1962), Bernard Epstein and Schiffer (1965), Myron Goldstein and Wellington (1971), who obtained a positive answer to this question under suitable additional assumptions. The problem was finally elegantly, completely and positively settled by Ülkü Kuran (1972), with an artful use of elementary techniques. This classical problem has been recently fleshed out by Giovanni Cupini, et al. (in press) who proved a quantitative stability result for the mean value formula, showing that a suitable "mean value gap" (measuring the normalized difference between the average of harmonic functions on a given set and their pointwise value) is bounded from below by the Lebesgue measure of the "gap" between the set and the ball (and, consequently, by the Fraenkel asymmetry of the set). That is, if a domain "almost" satisfies the mean value property for all harmonic functions, then that domain is "almost" a ball. The goal of this note is to investigate some nonlocal counterparts of these results. Some of our arguments rely on fractional potential theory, others on purely nonlocal properties, with no classical counterpart, such as the fact that "all functions are locally fractional harmonic up to a small error". [ABSTRACT FROM AUTHOR]

Published
2020
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