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Records with Keyword: Modelling
Extraction of Oil and Minor Compounds from Oil Palm Fruit with Supercritical Carbon Dioxide
Huan Phan Tai, Gerd Brunner
June 10, 2019 (v1)
Keywords: carotenoids, Modelling, supercritical extraction, tocopherols, tocotrienols
A significant quantity of tocochromanols and carotenoids remains in the residual from palm oil production by traditional screw pressing. Supercritical carbon dioxide extraction was used as alternative method with the purpose to recover better these valuable minor compounds. Total oil yield and co-extracted water were investigated in the course of extraction. Tocochromanols and carotenoids were evaluated, not only in the extraction oil, but also in the oil of residual fibre. Modelling of extraction process was also performed for a further up-scaling. The results showed that oil yield up to 90% could be observed within 120 min. Supercritical carbon dioxide (SCCO₂) could extract tocochromanols and carotenoids with concentration in the same range of normal commercial processing palm oil, while co-extracted water remained rather low at a level of 2⁻4%. Moreover, recovery efficiencies of these minor compounds were much higher in case of extraction processed with supercritical carbon dioxide... [more]
Accelerating Biologics Manufacturing by Modeling or: Is Approval under the QbD and PAT Approaches Demanded by Authorities Acceptable without a Digital-Twin?
Steffen Zobel-Roos, Axel Schmidt, Fabian Mestmäcker, Mourad Mouellef, Maximilian Huter, Lukas Uhlenbrock, Martin Kornecki, Lara Lohmann, Reinhard Ditz, Jochen Strube
June 10, 2019 (v1)
Subject: Biosystems
Keywords: biologics, continuous bioprocessing, manufacturing, Modelling, modular plants, Process Intensification, Renewable and Sustainable Energy
Innovative biologics, including cell therapeutics, virus-like particles, exosomes, recombinant proteins, and peptides, seem likely to substitute monoclonal antibodies as the main therapeutic entities in manufacturing over the next decades. This molecular variety causes a growing need for a general change of methods as well as mindset in the process development stage, as there are no platform processes available such as those for monoclonal antibodies. Moreover, market competitiveness demands hyper-intensified processes, including accelerated decisions toward batch or continuous operation of dedicated modular plant concepts. This indicates gaps in process comprehension, when operation windows need to be run at the edges of optimization. In this editorial, the authors review and assess potential methods and begin discussing possible solutions throughout the workflow, from process development through piloting to manufacturing operation from their point of view and experience. Especially,... [more]
Advances in Mathematical Modeling of Gas-Phase Olefin Polymerization
Mohd Farid Atan, Mohd Azlan Hussain, Mohammad Reza Abbasi, Mohammad Jakir Hossain Khan, Muhamad Fazly Abdul Patah
May 16, 2019 (v1)
Keywords: gas phase, kinetics, Modelling, olefin
Mathematical modeling of olefin polymerization processes has advanced significantly, driven by factors such as the need for higher-quality end products and more environmentally-friendly processes. The modeling studies have had a wide scope, from reactant and catalyst characterization and polymer synthesis to model validation with plant data. This article reviews mathematical models developed for olefin polymerization processes. Coordination and free-radical mechanisms occurring in different types of reactors, such as fluidized bed reactor (FBR), horizontal-stirred-bed reactor (HSBR), vertical-stirred-bed reactor (VSBR), and tubular reactor are reviewed. A guideline for the development of mathematical models of gas-phase olefin polymerization processes is presented.
FFANN Optimization by ABC for Controlling a 2nd Order SISO System’s Output with a Desired Settling Time
Aydın Mühürcü
April 9, 2019 (v1)
Keywords: ABC, buck converter, control, FFANN, Modelling, Optimization, settling time
In this study, a control strategy is aimed to ensure the settling time of a 2nd order system’s output value while its input reference value is changed. Here, Feed Forward Artificial Neural Network (FFANN) nonlinear structure has been chosen as a control algorithm. In order to implement the intended control strategy, FFANN’s normalization coefficient (K), learning coefficients (ŋ), momentum coefficients (μ) and the sampling time (Ts) were optimized by Artificial Bee Colony (ABC) but FFANN’s values of weights were chosen arbitrary on start time of control system. After optimization phase, the FFANN behaves as an adaptive optimal discrete time non-linear controller that forces the system output to take the same value with the input reference for a desired settling time (ts). The success of the optimization algorithm was proved with close loop feedback control simulations on Matlab’s Simulink platform based on 2nd order transfer functions. Also, the success was proved with a 2nd order phys... [more]
Mathematical Modeling of RBC Count Dynamics after Blood Loss
Manuel Tetschke, Patrick Lilienthal, Torben Pottgiesser, Thomas Fischer, Enrico Schalk, Sebastian Sager
April 8, 2019 (v1)
Subject: Biosystems
Keywords: erythropoiesis, Modelling, numerical simulation, parameter estimation, phlebotomy
The regeneration of red blood cells (RBCs) after blood loss is an individual complex process. We present a novel simple compartment model which is able to capture the most important features and can be personalized using parameter estimation. We compare predictions of the proposed and personalized model to a more sophisticated state-of-the-art model for erythropoiesis, and to clinical data from healthy subjects. We discuss the choice of model parameters with respect to identifiability. We give an outlook on how extensions of this novel mathematical model could have an important impact for personalized clinical decision support in the case of polycythemia vera (PV). PV is a slow-growing type of blood cancer, where especially the production of RBCs is increased. The principal treatment targeting the symptoms of PV is bloodletting (phlebotomy), at regular intervals that are based on personal experiences of the physicians. Model-based decision support might help to identify optimal and ind... [more]
Modeling of a Field-Modulated Permanent-Magnet Machine
Xianglin Li, K. T. Chau, Yubin Wang
February 27, 2019 (v1)
Keywords: d-q frame, field-modulated permanent magnet (FMPM) machine, finite element analysis (FEA), Modelling
In this work, an effective field-modulated permanent-magnet (FMPM) machine was investigated, in which the spoke-magnet outer rotor and open-slot stator were employed. The objective of this paper is to provide the mathematical modeling analysis that was performed for the purpose of control research on this type of FMPM machine. The simulation results by means of finite element analysis (FEA) are given to verify the theoretical analysis and the validity of mathematical model. A prototype machine was also fabricated for experimentation. Both the analytical model and the FEA results are validated by experimental tests on the prototype machine.
Lumped Parameters Model of a Crescent Pump
Massimo Rundo, Alessandro Corvaglia
January 31, 2019 (v1)
Keywords: crescent pump, fluid power, internal gear pump, Modelling
This paper presents the lumped parameters model of an internal gear crescent pump with relief valve, able to estimate the steady-state flow-pressure characteristic and the pressure ripple. The approach is based on the identification of three variable control volumes regardless of the number of gear teeth. The model has been implemented in the commercial environment LMS Amesim with the development of customized components. Specific attention has been paid to the leakage passageways, some of them affected by the deformation of the cover plate under the action of the delivery pressure. The paper reports the finite element method analysis of the cover for the evaluation of the deflection and the validation through a contactless displacement transducer. Another aspect described in this study is represented by the computational fluid dynamics analysis of the relief valve, whose results have been used for tuning the lumped parameters model. Finally, the validation of the entire model of the p... [more]
An Integer Linear Programming Model for an Ecovat Buffer
Gijs J. H. de Goeijen, Gerard J. M. Smit, Johann L. Hurink
January 7, 2019 (v1)
Subject: Optimization
Keywords: integer linear programming, Modelling, seasonal thermal storage, smart grids
An increase in the number of volatile renewables in the electricity grid enhances the imbalance of supply and demand. One promising candidate to solve this problem is to improve the energy storage. The Ecovat system is a new seasonal thermal energy storage system currently under development. In this paper, an integer linear programming model is developed to describe the behaviour and potential of this system. Furthermore, it is compared with a previously developed model, which is simplifying the behaviour of the Ecovat system much more, but is much less computationally expensive. It is shown that the new approach performs significantly better for several cases. For controlling a real Ecovat system in the future we may incorporate a number of improvements identified by our comparison analysis into the previously developed approach, which may help increase the quality of the obtained results without increasing the computational effort too much.
Modelling, Testing and Analysis of a Regenerative Hydraulic Shock Absorber System
Ruichen Wang, Fengshou Gu, Robert Cattley, Andrew D. Ball
November 27, 2018 (v1)
Keywords: Modelling, parameter identification, power regeneration, shock absorber, suspension
To improve vehicle fuel economy whilst enhancing road handling and ride comfort, power generating suspension systems have recently attracted increased attention in automotive engineering. This paper presents our study of a regenerative hydraulic shock absorber system which converts the oscillatory motion of a vehicle suspension into unidirectional rotary motion of a generator. Firstly a model which takes into account the influences of the dynamics of hydraulic flow, rotational motion and power regeneration is developed. Thereafter the model parameters of fluid bulk modulus, motor efficiencies, viscous friction torque, and voltage and torque constant coefficients are determined based on modelling and experimental studies of a prototype system. The model is then validated under different input excitations and load resistances, obtaining results which show good agreement between prediction and measurement. In particular, the system using piston-rod dimensions of 50⁻30 mm achieves recovera... [more]
Lithium Ion Batteries—Development of Advanced Electrical Equivalent Circuit Models for Nickel Manganese Cobalt Lithium-Ion
Alexandros Nikolian, Yousef Firouz, Rahul Gopalakrishnan, Jean-Marc Timmermans, Noshin Omar, Peter van den Bossche, Joeri van Mierlo
November 27, 2018 (v1)
Subject: Materials
Keywords: begin of life (BoL) parameters, cell characterization, dynamic discharge pulse test (DDPT), equivalent circuit model (ECM), lithium ion, Modelling, nickel manganese cobalt (NMC), validation profile, worldwide harmonized light vehicle test procedure (WLTC)
In this paper, advanced equivalent circuit models (ECMs) were developed to model large format and high energy nickel manganese cobalt (NMC) lithium-ion 20 Ah battery cells. Different temperatures conditions, cell characterization test (Normal and Advanced Tests), ECM topologies (1st and 2nd Order Thévenin model), state of charge (SoC) estimation techniques (Coulomb counting and extended Kalman filtering) and validation profiles (dynamic discharge pulse test (DDPT) and world harmonized light vehicle profiles) have been incorporated in the analysis. A concise state-of-the-art of different lithium-ion battery models existing in the academia and industry is presented providing information about model classification and information about electrical models. Moreover, an overview of the different steps and information needed to be able to create an ECM model is provided. A comparison between begin of life (BoL) and aged (95%, 90% state of health) ECM parameters (internal resistance (Ro), pola... [more]
A New Approach of Modeling an Ultra-Super-Critical Power Plant for Performance Improvement
Guolian Hou, Yu Yang, Zhuo Jiang, Quan Li, Jianhua Zhang
November 27, 2018 (v1)
Keywords: coordinated control system, Modelling, performance improvement, T-S fuzzy model, ultra super-critical power plant
A suitable model of coordinated control system (CCS) with high accuracy and simple structure is essential for the design of advanced controllers which can improve the efficiency of the ultra-super-critical (USC) power plant. Therefore, with the demand of plant performance improvement, an improved T-S fuzzy model identification approach is proposed in this paper. Firstly, the improved entropy cluster algorithm is applied to identify the premise parameters which can automatically determine the cluster numbers and initial cluster centers by introducing the concept of a decision-making constant and threshold. Then, the learning algorithm is used to modify the initial cluster center and a new structure of concluding part is discussed, the incremental data around the cluster center is used to identify the local linear model through a weighted recursive least-square algorithm. Finally, the proposed approach is employed to model the CCS of a 1000 MW USC one-through boiler power plant by using... [more]
Gas-Phase Mass-Transfer Resistances at Polymeric Electrolyte Membrane Fuel Cells Electrodes: Theoretical Analysis on the Effectiveness of Interdigitated and Serpentine Flow Arrangements
Elisabetta Arato, Marzia Pinna, Michela Mazzoccoli, Barbara Bosio
November 27, 2018 (v1)
Subject: Materials
Keywords: gas flow mode, Modelling, polymeric membrane fuel cells, transport phenomena
Mass transfer phenomena in polymeric electrolyte membrane fuel cells (PEMFC) electrodes has already been analyzed in terms of the interactions between diffusive and forced flows. It was demonstrated that the whole phenomenon could be summarized by expressing the Sherwood number as a function of the Peclet number. The dependence of Sherwood number on Peclet one Sh(Pe) function, which was initially deduced by determining three different flow regimes, has now been given a more accurate description. A comparison between the approximate and the accurate results for a reference condition of diluted reactant and limit current has shown that the former are useful for rapid, preliminary calculations. However, a more precise and reliable estimation of the Sherwood number is worth attention, as it provides a detailed description of the electrochemical kinetics and allows a reliable comparison of the various geometrical arrangements used for the distribution of the reactants.
Predictive Control Applied to a Solar Desalination Plant Connected to a Greenhouse with Daily Variation of Irrigation Water Demand
Lidia Roca, Jorge A. Sánchez, Francisco Rodríguez, Javier Bonilla, Alberto de la Calle, Manuel Berenguel
November 27, 2018 (v1)
Keywords: dynamic simulation, Modelling, multi-effect distillation, process control, solar energy
The water deficit in the Mediterranean area is a known matter severely affecting agriculture. One way to avoid the aquifers’ exploitation is to supply water to crops by using thermal desalination processes. Moreover, in order to guarantee long-term sustainability, the required thermal energy for the desalination process can be provided by solar energy. This paper shows simulations for a case study in which a solar multi-effect distillation plant produces water for irrigation purposes. Detailed models of the involved systems are the base of a predictive controller to operate the desalination plant and fulfil the water demanded by the crops.
Parameter Sensitivity Analysis for Fractional-Order Modeling of Lithium-Ion Batteries
Daming Zhou, Ke Zhang, Alexandre Ravey, Fei Gao, Abdellatif Miraoui
November 27, 2018 (v1)
Keywords: dynamic effects, fractional calculus, lithium-ion battery, Modelling, parameters sensitivity
This paper presents a novel-fractional-order lithium-ion battery model that is suitable for use in embedded applications. The proposed model uses fractional calculus with an improved Oustaloup approximation method to describe all the internal battery dynamic behaviors. The fractional-order model parameters, such as equivalent circuit component coefficients and fractional-order values, are identified by a genetic algorithm. A modeling parameters sensitivity study using the statistical Multi-Parameter Sensitivity Analysis (MPSA) method is then performed and discussed in detail. Through the analysis, the dynamic effects of parameters on the model output performance are obtained. It has been found out from the analysis that the fractional-order values and their corresponding internal dynamics have different degrees of impact on model outputs. Thus, they are considered as crucial parameters to accurately describe a battery’s dynamic voltage responses. To experimentally verify the accuracy o... [more]
Lifetime Prediction of a Polymer Electrolyte Membrane Fuel Cell under Automotive Load Cycling Using a Physically-Based Catalyst Degradation Model
Manik Mayur, Mathias Gerard, Pascal Schott, Wolfgang G. Bessler
September 21, 2018 (v1)
Keywords: catalyst degradation, driving cycle, durability estimation, Modelling, polymer electrolyte membrane fuel cell (PEMFC)
One of the bottlenecks hindering the usage of polymer electrolyte membrane fuel cell technology in automotive applications is the highly load-sensitive degradation of the cell components. The cell failure cases reported in the literature show localized cell component degradation, mainly caused by flow-field dependent non-uniform distribution of reactants. The existing methodologies for diagnostics of localized cell failure are either invasive or require sophisticated and expensive apparatus. In this study, with the help of a multiscale simulation framework, a single polymer electrolyte membrane fuel cell (PEMFC) model is exposed to a standardized drive cycle provided by a system model of a fuel cell car. A 2D multiphysics model of the PEMFC is used to investigate catalyst degradation due to spatio-temporal variations in the fuel cell state variables under the highly transient load cycles. A three-step (extraction, oxidation, and dissolution) model of platinum loss in the cathode cataly... [more]
DC/DC Boost Converter⁻Inverter as Driver for a DC Motor: Modeling and Experimental Verification
Víctor Hugo García-Rodríguez, Ramón Silva-Ortigoza, Eduardo Hernández-Márquez, José Rafael García-Sánchez, Hind Taud
September 21, 2018 (v1)
Keywords: bidirectional angular velocity, DC motor, DC/DC boost converter, differential flatness, experimental verification, inverter, Modelling
In this paper, the modeling and the experimental verification of the “bidirectional DC/DC boost converter⁻DC motor„ system are presented. By using circuit theory along with the model of a DC motor, the mathematical model of the system is derived. This model was experimentally tested under time-varying duty cycles obtained via the system differential flatness property. The experimental verification was carried out using Matlab-Simulink and a DS1104 board in a built prototype of the system.
Dry Fuel Jet Half-Angle Measurements and Correlation for an Entrained Flow Gasifier
Francis Kus, Robin Hughes, Arturo Macchi, Poupak Mehrani, Marc Duchesne
September 21, 2018 (v1)
Keywords: gasification, imaging, jet half-angle, Modelling
Reduced order models (ROMs) are increasingly applied to entrained flow gasification development due to reduced computational requirements relative to computational fluid dynamics (CFD) models. However, they require greater a posteriori knowledge of the reactor physics. A significant parameter influencing ROM outputs is the jet half-angle of the solid fuel and oxidant mixture in the gasifier. Thus, it is important to understand the geometry of the jet in the gasifier, and how it is dependent on operating parameters, such as solid and carrier gas flow rates. In this work, an existing model for jet half-angles, which considers the ratio of surrounding gas density to jet core density, is extended to a dry solids jet with impinging gas. The model is fitted to experimental jet half-angles. The jet half-angle of a non-reactive flow was measured using laser-sheet imaging for solid fluxes in the range of 460⁻880 kg/m²·s and carrier gas fluxes in the range of 43⁻90 kg/m²·s at the transport line... [more]
Aspen Plus Simulation of Biomass-Gas-and-Nuclear-To-Liquids (BGNTL) Processes (Using CuCl Route)
James Alexander Scott, Thomas Alan Adams II
August 7, 2018 (v1)
These are Aspen Plus simulation files for a Biomass-Gas-and-Nuclear-To-Liquids chemical plant (a conceptional design), which uses the Copper-Chloride route for hydrogen production. This is a part of a larger work (see linked LAPSE record for pre-print and associated publication in Canadian J Chem Eng). Process sections and major units in this simulation include: Gasification, Integrated-Gasification-Methane-Reforming, Pre-Reforming, Water Gas Shift, Autothermal Reforming, Syngas Blending and Upgrading, Solid Oxide Fuel Cell power islands, Fischer-Tropsch Synthesis, Methanol Synthesis, Dimethyl Ether Synthesis, Heat Recovery and Steam Generation, CO2 Compression for Sequestration, Cooling Towers, and various auxiliary units for heat and pressure management. See the linked work for a detailed description of the model.
Modelling the Nanomechanical Responses of Biofilms Grown on the Indenter Probe
Yuqing Xia, Pengfei Duan, Jinju Chen
July 31, 2018 (v1)
Keywords: biofilm, Modelling, nanoindentation
Biofilms have a profound impact on the environment, human health and industrial systems. In order to manage and control them, it is important to measure their mechanical properties intact. Therefore, it has been proposed to grow the biofilms on the atomic force microscope prior to nanoindentation tests with the same probe. However, for nanoindentation of biofilm grown on spherical indenter itself, the existing nanoindentation models become invalid. Therefore, modified models have been proposed to describe the nanoindentation response of biofilm grown on a sphere based on finite element modelling. It was found that the applicability of the models depends on the biofilm thickness and constitutive mechanical models adopted for biofilms. The models developed here would enable more reliable determination of viscoelastic properties of biofilms that grow intact on the indenter itself.
Systematic Design and Evaluation of an Extraction Process for Traditionally Used Herbal Medicine on the Example of Hawthorn (Crataegus monogyna JACQ.)
Maximilian Sixt, Jochen Strube
July 31, 2018 (v1)
Keywords: harvest, Modelling, pressurized hot water extraction, Simulation, variety
Traditionally used herbal medicines are deep in the consciousness of patients for the treatment of only minor diseases by self-medication. However, manufacturers of herbal medicinal products suffer from major problems such as increasing market pressure by e.g., the food supplement sector, increasing regulations, and costs of production. Moreover, due to more stringent regulation and approval processes, innovation is hardly observed, and the methods used in process development are outdated. Therefore, this study aims to provide an approach based on modern process engineering concepts and including predictive process modelling and simulation for the extraction of traditional herbal medicines as complex extracts. The commonly used solvent-based percolation is critically assessed and compared to the so-called pressurized hot water extraction (PHWE) as a new possible alternative to replace organic solvents. In the study a systematic process design for the extraction of hawthorn (Crataegus m... [more]
Bleaching of Neutral Cotton Seed Oil Using Organic Activated Carbon in a Batch System: Kinetics and Adsorption Isotherms
Abba Chetima, Abdoul Wahabou, Gaston Zomegni, Abdoul Ntieche Rahman, Divine Bup Nde
July 31, 2018 (v1)
Keywords: activated carbon, cotton, isotherms, Modelling, neem, oil bleaching
In the processing of cotton and neem seeds to obtain oil for diverse uses, enormous quantities of seed husk are generated as waste, which when not properly disposed of, poses environmental problems. One way of reducing this waste is to use it for the production of activated carbon (AC) for its multiple applications. In this work, activated carbon was produced from cotton and neem seed husks by carbonization followed by acid activation. The prepared ACs were characterized for its porosity and surface properties as well as for its ability to bleach neutral cotton seed oil. The prepared ACs are very efficient in the decoloration process, as they removed about 96⁻98% of the pigments compared to 98.4% removal with commercial bleaching earth. Temperature had a pronounced effect on the bleaching of neutral cotton seed oil. Maximum adsorption was observed at 60 °C for a contact time of 45 min. The adsorption kinetics were modelled by the intra-particle and the pseudo-second order equations whi... [more]
Systematic and Model-Assisted Evaluation of Solvent Based- or Pressurized Hot Water Extraction for the Extraction of Artemisinin from Artemisia annua L.
Maximilian Sixt, Jochen Strube
July 31, 2018 (v1)
Keywords: artemisinin, Extraction, Green Solvents, Modelling, Pressurized Hot Water Extraction, Simulation
In this study, the solvent based extraction of artemisinin from Artemisia annua L. using acetone in percolation mode is compared to the method of pressurized hot water extraction. Both techniques are simulated by a physico-chemical process model. The model as well as the model parameter determination, including the thermal degradation of artemisinin are shown and discussed. For the conventional extraction, a solvent screening is performed considering various organic solvents. A temperature screening is presented for the systematic design of the pressurized hot water extraction. The best temperature with regards to thermal decomposition and high productivity was found to be 80 °C. Both, conventional percolation and Pressurized Hot Water Extraction (PHWE) are suitable for the extraction of artemisinin. The extraction curves show a high conformity with the simulation results.
Aqueous Free-Radical Polymerization of Non-Ionized and Fully Ionized Methacrylic Acid
Eric Jean Fischer, Giuseppe Storti, Danilo Cuccato
July 31, 2018 (v1)
Subject: Materials
Keywords: electrostatic interactions, electrostatic screening, free radical polymerization, kinetics, methacrylic acid, Modelling, NMR, propagation, termination
Water-soluble, carboxylic acid monomers are known to exhibit peculiar kinetics when polymerized in aqueous solution. Namely, their free-radical polymerization rate is affected by several parameters such as monomer concentration, ionic strength, and pH. Focusing on methacrylic acid (MAA), even though this monomer has been largely addressed, a systematic investigation of the effects of the above-mentioned parameters on its polymerization rate is missing, in particular in the fully ionized case. In this work, the kinetics of non-ionized and fully ionized MAA are characterized by in-situ nuclear magnetic resonance (NMR). Such accurate monitoring of the reaction rate enables the identification of relevant but substantially different effects of the monomer and electrolyte concentration on polymerization rate in the two ionization cases. For non-ionized MAA, the development of a kinetic model based on literature rate coefficients allows us to nicely simulate the experimental data of conversio... [more]
Modeling of the Copolymerization Kinetics of n-Butyl Acrylate and d-Limonene Using PREDICI ®
Shanshan Ren, Eduardo Vivaldo-Lima, Marc A. Dubé
July 30, 2018 (v2)
Keywords: d-limonene, Modelling, n-butyl acrylate, polymerization kinetics
Kinetic modeling of the bulk copolymerization of d-limonene (Lim) and n-butyl acrylate (BA) at 80 °C was performed using PREDICI®. Model predictions of conversion, copolymer composition and average molecular weights are compared to experimental data at five different feed compositions (BA mol fraction = 0.5 to 0.9). The model illustrates the significant effects of degradative chain transfer due to the allylic structure of Lim as well as the intramolecular chain transfer mechanism due to BA.
Deterministic Global Optimization with Artificial Neural Networks Embedded
Global deterministische Optimierung von Optimierungsproblemen mit künstlichen neuronalen Netzwerken
Artur M Schweidtmann, Alexander Mitsos
October 15, 2018 (v2)
Subject: Optimization
Artificial neural networks (ANNs) are used in various applications for data-driven black-box modeling and subsequent optimization. Herein, we present an efficient method for deterministic global optimization of ANN embedded optimization problems. The proposed method is based on relaxations of algorithms using McCormick relaxations in a reduced-space [\textit{SIOPT}, 20 (2009), pp. 573-601] including the convex and concave envelopes of the nonlinear activation function of ANNs. The optimization problem is solved using our in-house global deterministic solver MAiNGO. The performance of the proposed method is shown in four optimization examples: an illustrative function, a fermentation process, a compressor plant and a chemical process optimization. The results show that computational solution time is favorable compared to the global general-purpose optimization solver BARON.
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