Application of mixed integer nonlinear programming for system identification

This work describes a method of deadtime approximation in dynamic systems, particularly in the context of nonlinear model predictive control based on mechanistic models where the differentiability of the equations must be ensured. The resulting system identification system is solved using the BBMCSFilter (Branch and Bound based on a Multistart Coordinate Search Filter) global optimization algorithm to determine the order and the parameters of the resulting model, taking into account not only the model-plant mismatch but also the model complexity and the resulting computation time. The application of the method is illustrated with a simulated example of a chemical process unit. © 2020 American Institute of Physics Inc.. All rights reserved.This work was supported by Fundac¸ao para a Ciência e a Tecnologia, UID/EQU/00102/2019. The first author also thanks project MATIS, ref. CENTRO-01-0145-FEDER-000014, with financial support of ERDF (CENTRO2020).info:eu-repo/semantics/publishedVersio

PID controllers tuning with MCSFilter

This work concerns the tuning of industrial controllers through the use of the Multistart Coordinate Search Filter algorithm. The task is laid as a bounded nonlinear global optimization problem aiming at achieving the best possible performance of the control loops at the lowest possible wearing of the costly valves. Moreover, the tuning was successfully carried out both with and without taking into consideration the existing interactions between different loops.info:eu-repo/semantics/publishedVersio

Application of MCSFilter to estimate stiction control valve parameters

The mitigation of the stiction phenomena in control valves is of paramount importance for efficient industrial plant operation. Mathematical models of sticky valves are typically discontinuous and highly nonlinear. A derivative-free optimization method is applied in the context of parameter estimation in order to determine the stiction parameters of a control valve. The method successfully determines the correct parameter set and compares favorably with a previous case study of this problem that used smooth function.info:eu-repo/semantics/publishedVersio

Using Sequential Quadratic Programming for System Identification

System identification plays an important role in the development of process simulators and controllers. The ability to determine correctly the model parameters directly affects the model quality and, therefore, the model based controller performance. This work details the development of a system identification approach and its computational implementation based on sequential quadratic programming (SQP) in which first and second order linear systems, represented in state-space, are identified from simulated and from real industrial process data. Both single-input single-output and multivariable processes are considered. The resulting optimization problem may become not trivial to solve as one of the examples illustrates. It is shown how a rescaling of the decision variables or the use of a priori process knowledge may be used in order to overcome the difficulties and to improve the quality of the results

Parameter estimation of a pulp digester model with derivative-free optimization strategies

The work concerns the parameter estimation in the context of the mechanistic modelling of a pulp digester. The problem is cast as a box bounded nonlinear global optimization problem in order to minimize the mismatch between the model outputs with the experimental data observed at a real pulp and paper plant. MCSFilter and Simulated Annealing global optimization methods were used to solve the optimization problem. While the former took longer to converge to the global minimum, the latter terminated faster at a significantly higher value of the objective function and, thus, failed to find the global solution.info:eu-repo/semantics/publishedVersio

Research of parameters of the steam boiler BKZ-220-100 at joint burning of natural gas and low-grade fuel

In this article the research of prospects of use of low-grade brown coal of the Talovsky Deposit of the Tomsk region as fuel for local power is carried out. The study is carried out by checking calculations of the steam boiler BKZ-220-100. The result of the study is to obtain data on the parameters of the boiler during the combustion of brown talovsky coal as the main fuel, as well as in a mixture with natural gas or Kuznetsk coal

Práticas formais, informais e de poder sombra no espaço político contemporâneo

The present paper considers various forms and practices of power-related interaction in the political system of modern society. It is noted that the institutional-normative and structural-functional aspects do not reflect the variety of forms and types of communication between public and power. The authors substantiate the methodological position according to which the activity of political subjects should not be considered in traditional theoretical and methodological coordinates, where attention is paid only to "positive phenomena", and power communication is not analyzed from the standpoint of "negative structures", i. e. those aspects which are not recognized as being fit into the dominant type of political and legal activity, into the framework of the emerging social order as a whole. The formal, informal, shadow and other power practices that exist in today's political space are considered in the work from this position.El presente trabajo considera diversas formas y prácticas de interacción relacionada con el poder en el sistema político de la sociedad moderna. Se observa que los aspectos institucional-normativos y estructural-funcionales no reflejan la variedad de formas y tipos de comunicación entre el público y el poder. Los autores corroboran la posición metodológica según la cual la actividad de los sujetos políticos no debe considerarse en las coordenadas teóricas y metodológicas tradicionales, donde la atención se centra únicamente en los "fenómenos positivos" y la comunicación de poder no se analiza desde el punto de vista de las "estructuras negativas", aquellos aspectos que no se reconocen como adecuados para el tipo dominante de actividad política y legal, en el marco del orden social emergente como un todo. Las prácticas formales, informales, de sombra y otras prácticas de poder que existen en el espacio político actual se consideran en el trabajo desde esta posición.O presente trabalho considera diversas formas e práticas de interação relacionadas ao poder no sistema político da sociedade moderna. Observa-se que os aspectos institucionais-normativos e estruturais-funcionais não refletem a variedade de formas e tipos de comunicação entre o público e o poder. Os autores confirmam a posição metodológica que a atividade de sujeitos políticos não deve ser considerada em coordenadas teóricas e metodológicas tradicionais, onde o foco é apenas sobre os "desenvolvimentos positivos" e comunicação de poder não é analisado do ponto de vista das "estruturas negativas", aqueles aspectos que não são reconhecidos como adequados ao tipo dominante de atividade política e legal, no contexto da ordem social emergente como um todo. As práticas formais, informais, sombra e outras práticas de poder que existem no espaço político atual são consideradas no trabalho a partir desta posição

Effects of Arctic commercial shipping on environments and communities : context, governance, priorities

Increasing shipping traffic in the Arctic Ocean creates an emerging need to understand the consequences of maritime operations on the Arctic environment and coastal Indigenous and non-Indigenous communities, as well as potential governance responses. To address this need, we examine recent shipping trends and assess their impact on Arctic environments and communities. Our arguments are novel, and are built around contemporary empirical investigations and published scientific studies, reports, and government documents. The paper concludes that the environmental and community impacts vary across the Arctic and that greater international coordination is needed to learn from experience, to share assets and capacities, and to guide responsible and sustainable development of Arctic shipping. Given the possibility for opening of the Transpolar Sea Route within the coming decades, further proactive steps, such as developing a governance framework, could help Arctic shipping avoid rather than attempt to correct problems. Shipping Arctic routes Indigenous peoples Local communities Social and environmental concerns RiskspublishedVersio

Influence of Titania Synthesized by Pulsed Laser Ablation on the State of Platinum during Ammonia Oxidation

A set of physicochemical methods, including X-ray photoelectron spectroscopy (XPS), X-ray diffraction, electron microscopy and X-ray absorption spectroscopy, was applied to study Pt/TiO$_{2}$ catalysts prepared by impregnation using a commercial TiO$_{2}$-P25 support and a support produced by pulsed laser ablation in liquid (PLA). The Pt/TiO$_{2}$-PLA catalysts showed increased thermal stability due to the localization of the highly dispersed platinum species at the intercrystalline boundaries of the support particles. In contrast, the Pt/TiO$_{2}$-P25 catalysts were characterized by uniform distribution of the Pt species over the support. Analysis of Pt4f XP spectra shows that oxidized Pt$^{2+}$ and Pt$^{4+}$ species are formed in the Pt/TiO$_{2}$-P25 catalysts, while the platinum oxidation state in the Pt/TiO$_{2}$-PLA catalysts is lower due to stronger interaction of the active component with the support due to strong interaction via Pt-O-Ti bonds. The Pt4f XP spectra of the samples after reaction show Pt$^{2+}$ and metallic platinum, which is the catalytically active species. The study of the catalytic properties in ammonia oxidation showed that, unlike the catalysts prepared with a commercial support, the Pt/TiO$_{2}$-PLA samples show higher stability during catalysis and significantly higher selectivity to N$_{2}$ in a wide temperature range of 200–400 °C

In situ probing of Pt/TiO2_{2} activity in low-temperature ammonia oxidation

The improvement of the low-temperature activity of the supported platinum catalysts in selective ammonia oxidation to nitrogen is still a challenging task. The recent developments in in situ/operando characterization techniques allows to bring new insight into the properties of the systems in correlation with their catalytic activity. In this work, near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) and operando X-ray absorption spectroscopy (XAS) techniques were applied to study Pt/TiO$_{2}$ catalysts in ammonia oxidation (NH$_{3}$ + O$_{2}$ reaction). Several synthesis methods were used to obtain samples with different size of Pt particles, oxidation state of Pt, and morphology of the support. Metal platinum particles on titania prepared by pulsed laser ablation in liquids exhibited the highest activity at lower temperatures with the temperature of 50% conversion of NH$_{3}$ being 150 °C. The low-temperature activity of the catalysts synthesized by impregnation can be improved by the reductive pretreatment. NAP-XPS and operando XANES data do not show formation of PtO$_{x}$ surface layers or PtO/PtO$_{2}$ oxides during NH$_{3}$ + O$_{2}$ reaction. Despite the differences in the oxidation state of platinum in the as-prepared catalysts, their treatment in the reaction mixture results in the formation of metallic platinum particles, which can serve as centers for stabilization of the adsorbed oxygen species. Stabilization of the bulk platinum oxide structures in the Pt/TiO$_{2}$ catalysts seems to be less favorable due to the metal–support interaction