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Helicoidal minimal surfaces in a conformally flat 3-space
Kellcio Oliveira Ara\'ujo,Ningwei Cui,Romildo da Silva Pina 대한수학회 2016 대한수학회보 Vol.53 No.2
In this work, we introduce the complete Riemannian manifold $\mathbb{F}_3$ which is a three-dimensional real vector space endowed with a conformally flat metric that is a solution of the Einstein equation. We obtain a second order nonlinear ordinary differential equation that characterizes the helicoidal minimal surfaces in $\mathbb{F}_3$. We show that the helicoid is a complete minimal surface in $\mathbb{F}_3$. Moreover we obtain a local solution of this differential equation which is a two-parameter family of functions $\lambda_{h,K_2}$ explicitly given by an integral and defined on an open interval. Consequently, we show that the helicoidal motion applied on the curve defined from $\lambda_{h,K_2}$ gives a two-parameter family of helicoidal minimal surfaces in $\mathbb{F}_3$.
HELICOIDAL MINIMAL SURFACES IN A CONFORMALLY FLAT 3-SPACE
Araujo, Kellcio Oliveira,Cui, Ningwei,Pina, Romildo da Silva Korean Mathematical Society 2016 대한수학회보 Vol.53 No.2
In this work, we introduce the complete Riemannian manifold $\mathbb{F}_3$ which is a three-dimensional real vector space endowed with a conformally flat metric that is a solution of the Einstein equation. We obtain a second order nonlinear ordinary differential equation that characterizes the helicoidal minimal surfaces in $\mathbb{F}_3$. We show that the helicoid is a complete minimal surface in $\mathbb{F}_3$. Moreover we obtain a local solution of this differential equation which is a two-parameter family of functions ${\lambda}_h,K_2$ explicitly given by an integral and defined on an open interval. Consequently, we show that the helicoidal motion applied on the curve defined from ${\lambda}_h,K_2$ gives a two-parameter family of helicoidal minimal surfaces in $\mathbb{F}_3$.
Intelligent control system for extractive distillation columns
Thiago Gonçalves das Neves,Wagner Brandão Ramos,Gilvan Wanderley de Farias Neto,Romildo Pereira Brito 한국화학공학회 2018 Korean Journal of Chemical Engineering Vol.35 No.4
We developed and implemented an intelligent control system to be used in an extractive distillation column that produces anhydrous ethanol using ethylene glycol as solvent. The concept of artificial neural networks (ANN) was used to predict new setpoints after disturbances, and proved to be a fast and feasible solution. The developed control system receives data from temperature, flowrate and composition measurements of the azeotrope feed, and the ANN estimates the new set-points of the controllers to maintain 99.5mol% of ethanol at the top and less than 0.1mol% at the bottom; feed composition was also estimated using an ANN. All ANN were trained to provide output data corresponding to an optimized operating condition. The results showed that the intelligent control system can predict a new operating condition for any disturbance in the column feed and presented superior performance when compared with the control system without ANN.
Modeling refractory concrete lining of fluid catalytic cracking units of oil refineries
Ana B.C.G. Silva,Henrique C.C. Andrade,Eduardo M.R. Fairbairn,Jose C.F. Telles,Fernando L.B. Ribeiro,Romildo D. Toledo-Filho,Jorivaldo Medeiros 사단법인 한국계산역학회 2020 Computers and Concrete, An International Journal Vol.25 No.1
This work presents a numerical modeling procedure to simulate the refractory concrete lining in fluid catalytic cracking units of oil refineries. The model includes the simulation of the anchors that reinforce the contact between the refractory concrete and the steel casing. For this purpose, the constitutive relations of an interface finite element are set to values that represent the homogenized behavior of the anchored interface. The parameters of this constitutive relation can be obtained by experimental tests. The model includes also multi-surface plasticity, in order to represent the behavior of the refractory concrete lining. Since the complexity of real case applications leads to high computational costs, the models presented here were implemented in a high-performance parallelized finite element platform. A case study representing a riser similar to the ones used by the refinery industry demonstrates the potential of the model.