Banca de DEFESA: NICÉIAS SILVA VILELA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : NICÉIAS SILVA VILELA
DATE: 23/02/2024
TIME: 09:00
LOCAL: https://meet.google.com/kum-jzpd-pmv
TITLE:

Use of Visibility Graph for analisys of soil computerized tomography images

KEY WORDS:

Visibility Graph, Computed Tomography, Soil.

PAGES: 44
BIG AREA: Ciências Agrárias
AREA: Agronomia
SUMMARY:

Soil has been increasingly studied due to its structure playing a vital role in sustainable food production and the well-being of society, mainly. In this sense, there is a growing search for a more holistic approach to land use and management to deal with the increasing pressure on soil resources for the production of food and, at the same time, reduce the adverse environmental impacts of agricultural practices. Such structure, which can be described as the spatial arrangement or heterogeneity of soil particles, aggregates and voids or pores, determines the functionality and sustainability of this living natural entity essential for the earth to fulfill its function. Recent advances in non-destructive imaging techniques, such as X-ray computed tomography (CT), make it possible to examine pore space characteristics through direct observation of soil structure. A quantitative characterization of the three-dimensional architecture of soil morphology is crucial to understanding soil mechanics as it relates to the control of biological, chemical, and physical processes at all scales. Despite improvements in the resolution of computed tomography equipment and computational power, there is no consensus on data analysis methods that allow revealing the complexity of all elements associated with 3D soil images, especially methods that do not require a threshold to segment images. In this work, we propose an approach to study the morphological properties of soil and analyze changes in soil structure due to the disturbance caused by current sugarcane management techniques, which causes changes in its structure, mainly in the upper layer; for this, we use the Visibility Graph (VG) and Horizontal Visibility Graph (HVG) methods, based on the theory of complex networks, which converts time series into graphs through a geometric visibility criterion that associates each data in the time series to a node in the visibility graph. To date, these two methods have not been used in 3D image analysis. Analysis of the changes occurring in the structure is possible by comparing computed tomography images of the soil with Atlantic Forest and sugar cane coverage. VG and HVG are applied to columns of voxels in the gravity direction (Z) producing the planar (XY) distribution of topological indices. For each column of voxels VG and HVG networks were generated, and the Clustering Coefficient C, the Average Shortest Path Length ⟨d_ij ⟩, and the Average Degree ⟨k⟩ were calculated, which are indices used to describe the network topology. Promising results were obtained with two soil samples, the first of which consists of a computerized image of soil with Atlantic Forest cover, and another of sugar cane, both with a depth of 0-10cm, were used to show the efficiency of the methods applied. In terms of comparing the application of the HVG and VG methods both performed for each vertical column of voxels proved to be efficient and produced very competitive results. The index Average shortest path length of the HVG network and the Average degree of the VG network showed the greatest difference between the samples, showing that these indices are efficient and suitable for quantifying the degradation of soil morphological properties caused by changes in vegetation cover.

COMMITTEE MEMBERS:
Presidente - BORKO STOSIC
Externo à Instituição - JOSÉ DOMINGOS ALBUQUERQUE AGUIAR - IFPE
Interno - LUCIAN BOGDAN BEJAN