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Federal University of Roraima

Education
About: Federal University of Roraima is a based out in . It is known for research contribution in the topics: Population & Thermogravimetry. The organization has 981 authors who have published 1218 publications receiving 7849 citations. The organization is also known as: Federal University of Roraima.


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Journal ArticleDOI
02 Jun 2021-Energies
TL;DR: A mixed-integer linear programming (MILP) model aiming at the optimal operation of the SBs and the appliance usage of each prosumer, as well as a PV plant within a community to achieve the maximum load factor (LF) increase is proposed.
Abstract: In prosumers’ communities, the use of storage batteries (SBs) as support for photovoltaic (PV) sources combined with coordination in household appliances usage guarantees several gains. Although these technologies increase the reliability of the electricity supply, the large-scale use of home appliances in periods of lower solar radiation and low electricity tariff can impair the performance of the electrical system. The appearance of new consumption peaks can lead to disturbances. Moreover, the repetition of these events in the short term can cause rapid fatigue of the assets. To address these concerns, this research proposes a mixed-integer linear programming (MILP) model aiming at the optimal operation of the SBs and the appliance usage of each prosumer, as well as a PV plant within a community to achieve the maximum load factor (LF) increase. Constraints related to the household appliances, including the electric vehicle (EV), shared PV plant, and the SBs, are considered. Uncertainties in consumption habits are simulated using a Monte Carlo algorithm. The proposed model was solved using the CPLEX solver. The effectiveness of our proposed model is evaluated with/without the LF improvement. Results corroborate the efficient performance of the proposed tool. Financial benefits are obtained for both prosumers and the energy company.

11 citations

Journal ArticleDOI
TL;DR: The authors avaliou o efeito do uso de dois corretivos de acidez do solo e de doses crescentes de fosforo, sobre a nodulacao, producao de materia seca, acumulos e teores dos nutrientes nas raizes do estilosantes Mineirao (Stylosanthes guianensis) Sw. cv.
Abstract: Objetivou-se, com este trabalho, avaliar o efeito do uso de dois corretivos de acidez do solo e de doses crescentes de fosforo, sobre a nodulacao, producao de materia seca, acumulos e teores dos nutrientes nas raizes do estilosantes Mineirao (Stylosanthes guianensis (Aubl.) Sw. cv. Mineirao). O experimento foi conduzido em casa-de-vegetacao com delineamento experimental em blocos casualizados, com tres repeticoes. Os tratamentos foram dispostos em esquema fatorial 5x2, constituido por cinco doses de P (50, 100, 200, 400 e 800 mg dm-3 de solo) e dois tipos de corretivo (calcario dolomitico e silicato de Ca e Mg). A producao de materia seca de raizes, a nodulacao e o acumulo dos nutrientes P, N, Ca e Zn foram maiores quando a adubacao esteve associada ao silicato. Entretanto, a aplicacao de doses superiores a 257 mg dm-3 de P na presenca de silicato, inibiu o desenvolvimento do sistema radicular do Mineirao, provavelmente por causa de uma interacao negativa entre os nutrientes P e Zn, causada pela alta disponibilidade de P.

11 citations

Journal ArticleDOI
01 Apr 2010
TL;DR: In this paper, the tomato crop with organic fertilization was evaluated in two experiments conducted at two times: spring/summer and autumn/spring, at the horticulture experimental field of the Universidade Federal de Vicosa in a Cambic Red-Yellow Argisol.
Abstract: Nitrogen fertilization efficiency in tomato at two sowing times Nitrogen fertilization efficiency of the tomato crop, with organic fertilization, was evaluated in two experiments conducted at two times: spring/summer and autumn/spring. The experiments were carried out at the horticulture experimental field of the Universidade Federal de Vicosa in a Cambic Red-Yellow Argisol. In both times, the applied N doses, in the form of nitrocalcium, were 0.0, 93.3, 187.0, 374.0 and 748.0 kg/ha and the doses of organic fertilization, in the form of cattle manure compost, were 0 and 8 t/ha of dry matter. The experiments were arranged in randomized blocks, in a 5 x 2 factorial design, with four replications. The weight and the number of marketed tomatoes per plant increased with the increase of N level in the soil. The percentage of commercially discarded fruits was larger in the spring/summer than in the autumn/spring. The nitrogen fertilization efficiency in tomato crop is higher in the autumn/ spring than in the spring/summer. In the spring/summer, the efficiency was higher without the addition of organic matter to the soil, whereas in the autumn/spring the opposite took place.

11 citations

Journal ArticleDOI
TL;DR: In this paper, the authors evaluate and compare the soil physical attributes of an Argissolo Amarelo (Ultisol) under savanna and forest natural ecosystems, and their conversion into a cattle pasture system.
Abstract: The broad soil and ecosystem diversity of the state of Roraima is gradually being replaced by pasture and, depending on the management system adopted, this can be associated with soil physical degradation. Within this context, the aim of the present study was to evaluate and compare the soil physical attributes of an Argissolo Amarelo (Ultisol) under savanna and forest natural ecosystems, and their conversion into a cattle pasture system. The primary treatments were natural savanna (NS), savanna converted to pasture (CS), natural forest (NF) and forest converted to pasture (CF). The secondary treatments were the soil sampling depths of 0-10, 10-20 and 20-40 cm. The following physical properties were evaluated: texture, bulk density (SD) and particle density (PD), resistance to penetration (PR), total porosity (TP), gravimetric moisture (GM), available water capacity (AWC), and soil organic matter (SOM). The SD was greater in both savanna areas, without differences between CS and NS at any depth, associated with the cohesive character of savanna soils. The average PD value was typical of kaolinite soils. PR varied as a function of the areas and the depths; the effect of conversion on this property was observed. TP was greater in NF and less in CS, and TP decreased along with depth. AWC was greater in NF only at the 0-10 cm depth. SOM was greater in the NF and CF areas. The study concluded that conversion of the natural environment into pasture systems caused significant changes in PR, SD, AWC, TP and SOM, with major expressiveness in CF, due to the removal of natural vegetation, leading to the loss of SOM, which is an important conditioner of soil physical and water properties. In CS areas, suppression of the natural vegetation did not lead to the same expressiveness, mainly due to the significantly lower SOM contents.

11 citations

Journal ArticleDOI
TL;DR: The Connectedness to Nature Scale mostrou ser uma medida psicometricamente adequada for avaliar um fator geral de conexao com a natureza, podendo ser empregada em estudos futures as mentioned in this paper.
Abstract: Este artigo objetivou reunir evidencias de validade e precisao da Connectedness to Nature Scale no contexto brasileiro. Dois estudos foram realizados. No Estudo 1, participaram 204 pessoas com idade media de 33 anos (Desvio-Padrao = 13,83), as quais responderam a referida escala e perguntas demograficas. Os resultados de uma analise de componentes principais indicaram uma estrutura unifatorial (a = 0,81). No Estudo 2, participaram 220 estudantes universitarios com idade media de 23 anos (Desvio-Padrao = 5,82), os quais responderam a escala adaptada e perguntas demograficas. Uma analise fatorial confirmatoria (estimador ML) confirmou a adequacao da estrutura unifatorial (e.g., Comparative Fit Index = 0,91, Root-Mean-Square Error of Approximation = 0,064), obtendo consistencia interna satisfatoria (a = 0,83). Concluindo, a Connectedness to Nature Scale mostrou ser uma medida psicometricamente adequada para avaliar um fator geral de conexao com a natureza, podendo ser empregada em estudos futuros.

10 citations


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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
20232
20222
2021125
2020183
201992
201899