Navegando por Data de Publicação, começando com "2020-08-03"

Filtrar resultados por ano ou mês

Agora exibindo 1 - 3 de 3

Conditional independence testing, two sample comparison and density estimation using neural networks
(Universidade Federal de São Carlos, 2020-08-03) Inacio, Marco Henrique de Almeida; Izbicki, Rafael; https://lattes.cnpq.br/9991192137633896; https://lattes.cnpq.br/1931901020027887
Given the vast amount of data available nowadays and the rapid increase of computational processing power, the field of machine learning and the so called algorithmic modeling have seen a recent surge in its popularity and applicability. One of the tools which has attracted great popularity is artificial neural networks due, to among other things, their versatility, ability to capture complex relations and computational scalability. In this work, we therefore apply such machine learning tools into three important problems of Statistics: two-sample comparison, conditional independence testing and conditional density estimation.
Identificação e classificação de áreas úmidas costeiras relacionadas à valoração de seus serviços ecossistêmicos na ilha de Santa Catarina (Florianópolis) – Brasil
(Universidade Federal de São Carlos, 2020-08-03) Teixeira, Marcela Ribeiro e Silva; Hennemann, Mariana Coutinho; https://lattes.cnpq.br/5417820950612976; Pires, José Salatiel Rodrigues; https://lattes.cnpq.br/3412204514901170; https://lattes.cnpq.br/4619471971970485
The uncontrolled growth of the population occurs mainly in coastal areas, resulting in a new form of appropriation of nature that intensifies and change the characteristics of the landscape. The impact caused becomes dangerous for the conservation of ecosystems, mainly coastal wetlands and their ecosystem services, which even covering 1.5% of the earth’s surface, represent 40% of the essential natural services offered to humanity. The services offered include, among others: periodic water supply; retention of flood pulses and sediments; purifies water; aquifer recharge and groundwater. The conservation of these areas guarantees the survival and well-being of humans and the ecosystem. For this, however, it is necessary to have reliable information to generate public policies that keep them conserved. Thus, the work aims to identify, measure and compare the coastal wetlands of Santa Catarina Island within the boundary of the Jurerê and Ratones hydrographic basins, in the years 1957 and 2016, relating them to their available ecosystem services using the valuation as an indicator. Monetary value of these services. For this purpose, a dichotomous switch was made to identify the coastal wetlands found through QGIS, to later identify ecosystem services with the help of the CICES V5.1 system, and finally to value the services through the transfer of benefits. A loss of 33.86% was observed in coastal wetlands in the 59-year interval and consequently there was a loss of 38,523,225.36 (R $ / ha / year) in ecosystem services. To regularize public policies that value the conservation of the environment, it is necessary to understand how it works, what it can provide for society and how it has been affected by the demographic growth of the region. Therefore, it is extremely important to identify and classify areas of social and biological interest, their available services, and the negative impacts brought to the population, serving as an argumentative basis for their conservation.
Estudo teórico de nano sistemas de azulenos: azulfenos, ANTs, poliazulenos e polinaftalenos
(Universidade Federal de São Carlos, 2020-08-03) Costa, Alexandre; López-Castillo, Alejandro; https://lattes.cnpq.br/2599181118729458; https://lattes.cnpq.br/4811445469385118
Azulene-based nanographene-like materials are predicted and studied to reveal the molecular properties of these new materials. C48H18/(G-48), C68H22/(G-68), and C88H26/(G-88) nanographenes and their isomers based on azulene molecule (azulphene) as A-48, A-68, and A-88 were studied to infer general properties for large azulphene systems. Nanotubes from azulphenes are also obtained and studied. The isoelectronic graphene and azulphene materials have significant differences concerning, e.g., electric dipole, aromaticity, bond length, and bond stress. In the present studies, it was used the Density Functional Theory (DFT) and including the version of Grimme´s D dispersion for the different spin multiplicities: singlet close-shell (CS) and open-shell (OS), triplet, and quintet. For example, the ground-state of A-(48-68-88) structures is a singlet. The UV-visible spectra of all compounds exhibit maximum absorption peaks attributed to the electronic transition π→π*. The IR spectrum of G-88 and A-88 shows an intense set of absorption peaks in the range [600:1700 cm-1]. The following IR frequencies could be used as an indicator of azulphene structures: 1124, 1162, 1436, 1542, and 1597 cm-1. The azulphene sheets have a non-uniform distribution of the electron density, unlike graphene systems, which makes them promising candidates for regioselective chemical modification. The nucleus independent chemical shift calculations show that the five-membered rings are aromatic, and the seven-membered rings are anti-aromatic similar to azulene molecule. Our study also showed that smaller diameter tubes based on azulene (C57NTs) might be more stable than their conventional C6NTs isomer. The geometries, the electronic structures and the aromaticity of the [n]-azulene and [n]-naphthalene polymers were studied, by using the Density Functional Theory (DFT) and the Møller–Plesset (MP2) Pertubation Theory, for the different multiplicities (M=2S+1): singlet (S=0, closed and open shell), triplet (S=1) and quintet (S=2). The ground-states of the [n]-azulene polymers were a singlet (closed shell) for any values of n (n≤10). The ground-states of the [n]-naphthalene polymers were a singlet (closed shell) for n≤6 and triplet for 7≤n≤10. The electric dipole moment of the odd [n]-azulene polymers varied with the length of the polymer chain, while exhibiting a local minimum for [5]-azulene. The dipole of the even [n]-azulene and the (even and odd) [n]-naphthalene polymers were null by symmetry, essentially as a result of the non-polar structure of the azulene dimer and the benzene molecule. The [n]-azulene polymers could be considered as semiconductors, since for the large chain, the HOMO-LUMO gap was estimated at 0.70 eV. The large naphthalene polymers perhaps reached zero gaps. All of the polymers had electronic transition peaks in the visible region and their maximum was red-shifted for the increasing chains. The nucleus independent chemical shift (NICS) calculations have shown that ring tension was an important factor in the aromaticity loss, as shown, for example, for the flat, the cycle, and the Möbius strip [20]-polymers. The Aromatic Stabilization Energies (ASEs) that were based on the homodesmotic and isodesmic reactions were also obtained.