Optimization on industrial problems focussing on multi-player strategies

Algorithms (EA) are useful optimization methods for exploration of the search space, but they usually have slowness problems to exploit and converge to the minimum with accuracy. On the other hand, gradient based methods converge faster to local minimums, although are not so robust (e.g., flat areas and discontinuities can cause problems) and they lack exploration capabilities. This thesis presents and analyze four versions of a hybrid optimization method trying to combine the virtues of Evolutionary Algorithms (EA) and gradient based algorithms, and to overcome their corresponding drawbacks. The proposed Hybrid Methods enables working with N optimization algorithms (called players), multiple objective functions and design variables, and define them differently for each player. The performance of the Hybrid Methods are compared against a gradient based method, two Genetic Algorithms (GA) and a Particle Swarm Optimization (PSO). Tests have been conducted with mathematical benchmark problems (synthetic tests designed to specifically test optimization methods) and an engineering application with high demanding computational resources, a Synthetic Jet actuator for Active Flow Control (AFC) over a 2D Selig-Donovan 7003 (SD7003) airfoil at Reynolds number 6 x 10^4 and a 14 degree angle of attack. The Active Flow control problem has been used in a single optimization problem and in a two objective optimization problemEls Algoritmes Evolutius (EA) són mètodes d'optimització útils per a l'exploració de l'espai de cerca, però solen tenir problemes de lentitud per explotar-ne el mínim i convergir amb precisió. D'altra banda, els mètodes basats en gradients convergeixen més ràpidament als mínims locals, encara que no són tan robusts (per exemple, les àrees planes i les discontinuïtats poden causar problemes) i no tenen capacitats d'exploració. Aquesta tesi presenta i analitza quatre versions d'un mètode d'optimització híbrid que intenta combinar les virtuts dels Algoritmes Evolutius (EA) i els algoritmes basats en gradients, i superar-ne els inconvenients corresponents. Els Mètodes Híbrids proposats permeten treballar amb N algoritmes d'optimització (anomenats jugadors), múltiples funcions objectiu i variables de disseny, i definir-les de manera diferent per a cada jugador. El rendiment dels mètodes híbrids es compara amb un mètode basat en gradient, dos Algoritmes Genètics (GA) i un mètode d'optimització d'eixam de partícules (PSO). S'han fet proves amb problemes matemàtics de referència (proves sintètiques dissenyades per provar específicament mètodes d'optimització) i una aplicació d'enginyeria amb recursos computacionals molt exigents, un actuador de jet sintètic per a control de flux actiu (AFC) sobre un perfil aerodinàmic 2D Selig -Donovan 7003 (SD7003) al número de Reynolds 6 x 104 i un angle d'atac de 14 graus. El problema de control de flux actiu s'ha utilitzat en un problema d'optimització monoobjectiu i en un problema d'optimització de dos objectius.Postprint (published version

Estudi amb CFD de la cavitació en una turbina Francis

La finalitat d’aquest treball de fi de grau és estudiar mitjançant tècniques de mètodes numèrics els efectes produïts per l’aparició de cavitació en una turbina Francis. Per tal de reduir el cost computacional s’utilitza un model geomètric semblant a escala reduïda de les dimensions i característiques de treball de la turbina Francis de la central hidroelèctrica de Sallente. Mitjançant el software ANSYS CFX 16.2 es dur a terme la simulació del flux multi fàsic de líquid i vapor amb el model Zwart-Gerber-Belamri (ZGB) a partir dels resultats adquirits de la resolució per aproximació de les equacions de Navier-Stokes (RANS) el model de turbulència k-ω Shear-Stress Transport (SST) en les mateixes condicions. Per detectar els efectes s’han utilitzat gràfics de contorns que representen visualment diferents propietats, a més de gràfics de pressions en el temps, comparant els valors de la simulació sense utilitzar el model de cavitació respecte a la seva utilització. Obtenint resultats de comportament completament diferents en les dues simulacions

Disseny d'una aeronau no tripulada per al desenvolupament i assaig de sistemes d'abord

En aquest projecte es porta a terme el disseny preliminar d'una aeronau no tripulada destinada al desenvolupament i assaig de sistemes d'abord (Unmanned Air Systems UAS). Els requeriments operacionals han estat proposats pel grup d'investigació ICARUS de l'Escola d'Enginyeria de Telecomunicació Aeroespacial de Castelldefels (EETAC) i tenen en compte les seves necessitats de utilització així com certes característiques particulars difícils de trobar als models comercials disponibles. A més, per al disseny s'ha tingut en compte el marc regulador d'aeronaus no tripulades per a ús civil més recent, el Real Decreto-ley 8/2014 del 4 de juliol, que ha estat publicat durant el desenvolupament d'aquest treball. El treball s'organitza de la següent manera. En primer lloc es presenta una breu revisió de l'evolució dels UAVs i de les característiques principals dels models de ús civil que s'emplean en l'actualitat. A més a més, es presenten els requeriments operacionals proposats pel grup d'investigació ICARUS i els aspectes més destacats del marc legislatiu que puguin afectar el disseny de l'aeronau. A continuació es realitza el disseny conceptual de l'aeronau. Partint dels estudis dels requeriments, i revisant els diferents aspectes per determinar possibles punts conflictius amb els requeriments, es realitza el dimensionament bàsic de les parts principals que composen l'UAV. Els següents capítols aprofundeixen més en el disseny aerodinàmic, estructural, l'electrònica i les actuacions de l'aeronau. Per últim, es presenta un pressupost del projecte i les conclusion

Multi-objective design optimisation of a 3D-rail stamping process using a robust multi-objective optimisation platform (RMOP)

The paper investigates the multi-objective design optimisation of a stamping process to control the final shape and the final quality using advanced high strength steels. The design problem of the stamping process is formulated to minimise the difference between the desired shape and the final geometry obtained by numerical simulation accounting elastic springback. In addition, the final product quality is maximised by improving safety zones without wrinkling, thinning, or failure. Numerical results show that the proposed methodology improves the final product quality while reduces its springback.Peer ReviewedPostprint (published version

Posada al dia del mètode de classificació taxonòmica del circovirus porcí tipus 2

Un equip internacional i multidisciplinar de científics ha publicat un estudi al Virology Journal on s'estudia la classificació taxonòmica del circovirus porcí tipus 2 (PCV2), un dels principals patògens que afecten el sector porcí a nivell mundial.Un equipo internacional y multidisciplinar de científicos han publicado un estudio en el Virology Journal donde se estudia la clasificación taxonómica del circovirus porcino tipo 2 (PCV2), uno de los principales patógenos que afectan al sector porcino a nivel mundial. El estudio ha contado con la participación destacada de dos investigadores del IRTA- CReSA, el profesor Joaquim Segalés, del Departamento de Sanidad y Anatomía Animales de la UAB, y el doctor Martí Cortey, del subprograma de enfermedades endémicas del IRTA-CReSA.A multidisciplinary international team of scientists have published a study in Virology Journal revisiting the taxonomic classification of porcine circovirus type 2 (PCV2), one of the major pathogens affecting the pig industry worldwide. The study included the participation of two prominent researchers from the IRTA-CReSA, Professor Joaquim Segalés, from the Department of Animal Health and Anatomy at the UAB, and Dr. Martí Cortey, from the endemic diseases subprogram at IRTA-CReSA

Transmissibility, hospitalization, and intensive care admissions due to omicron compared to delta variants of SARS-CoV-2 in Catalonia: A cohort study and ecological analysis

COVID-19; Cohorts; SeverityCOVID-19; Cohorts; GravetatCOVID-19; Cohortes; GravedadPurpose: We aim to compare the severity of infections between omicron and delta variants in 609,352 SARS-CoV-2 positive cases using local hospitalization, vaccination, and variants data from the Catalan Health Care System (which covers around 7. 8 million people). Methods: We performed a substitution model to establish the increase in transmissibility of omicron using variant screening data from primary care practices (PCP) and hospital admissions. In addition, we used this data from PCP to establish the two periods when delta and omicron were, respectively, dominant (above 95% of cases). After that, we performed a population-based cohort analysis to calculate the rates of hospital and intensive care unit (ICU) admissions for both periods and to estimate reduction in severity. Rate ratios (RR) and 95% confidence intervals (95% CI) were calculated and stratified by age and vaccination status. In a second analysis, the differential substitution model in primary care vs. hospitals allowed us to obtain a population-level average change in severity. Results: We have included 48,874 cases during the delta period and 560,658 during the omicron period. During the delta period, on average, 3.8% of the detected cases required hospitalization for COVID-19. This percentage dropped to 0.9% with omicron [RR of 0.46 (95% CI: 0.43 to 0.49)]. For ICU admissions, it dropped from 0.8 to 0.1% [RR 0.25 (95% CI: 0.21 to 0.28)]. The proportion of cases hospitalized or admitted to ICU was lower in the vaccinated groups, independently of the variant. Omicron was associated with a reduction in risk of admission to hospital and ICU in all age and vaccination status strata. The differential substitution models showed an average RR between 0.19 and 0.50. Conclusion: Both independent methods consistently show an important decrease in severity for omicron relative to delta. The systematic reduction happens regardless of age. The severity is also reduced for non-vaccinated and vaccinated groups, but it remains always higher in the non-vaccinated population. This suggests an overall reduction in severity, which could be intrinsic to the omicron variant. The fact is that the RR in ICU admission is systematically smaller than in hospitalization points in the same direction.MC received funding from la Caixa Foundation ID 100010434, under agreement LCF/PR/GN17/50300003. MC, CP, and SA received funding from Ministerio de Ciencia, Innovación y Universidades and FEDER, with the project PGC2018-095456-B-I00

Multi-objective design optimisation of a 3D-rail stamping process using a robust multi-objective optimisation platform (RMOP)

The paper investigates the multi-objective design optimisation of a stamping process to control the final shape and the final quality using advanced high strength steels. The design problem of the stamping process is formulated to minimise the difference between the desired shape and the final geometry obtained by numerical simulation accounting elastic springback. In addition, the final product quality is maximised by improving safety zones without wrinkling, thinning, or failure. Numerical results show that the proposed methodology improves the final product quality while reduces its springback

A New Hybrid Optimization Method, Application to a Single Objective Active Flow Control Test Case

Genetic Algorithms (GA) are useful optimization methods for exploration of the search space, but they usually have slowness problems to exploit and converge to the minimum. On the other hand, gradient based methods converge faster to local minimums, although are not so robust (e.g., flat areas and discontinuities can cause problems) and they lack exploration capabilities. This article presents a hybrid optimization method trying to combine the virtues of genetic and gradient based algorithms, and to overcome their corresponding drawbacks. The performance of the Hybrid Method is compared against a gradient based method and a Genetic Algorithm, both used alone. The rate of convergence of the methods is used to compare their performance. To take into account the robustness of the methods, each one has been executed more than once, with different starting points for the gradient based method and different random seeds for the Genetic Algorithm and the Hybrid Method. The performance of the different methods is tested against an optimization Active Flow Control (AFC) problem over a 2D Selig–Donovan 7003 (SD7003) airfoil at Reynolds number 6×104 and a 14 degree angle of attack. Five design variables are considered: jet position, jet width, momentum coefficient, forcing frequency and jet inclination angle. The objective function is defined as minus the lift coefficient (-Cl), so it is defined as a minimization problem. The proposed Hybrid Method enables working with N optimization algorithms, multiple objective functions and design variables per optimization algorithm.This research has been partially supported through the Severo Ochoa Centre of Excellence (2019-2023) under the grant CEX2018-000797-S funded by MCIN/AEI/10.13039/501100011033. The third author, Jordi Pons-Prats, is a Serra Hunter Fellow.Peer ReviewedObjectius de Desenvolupament Sostenible::13 - Acció per al ClimaObjectius de Desenvolupament Sostenible::9 - Indústria, Innovació i InfraestructuraPostprint (published version

A case of uterine inclusion cysts in a sow

Serosal inclusion cysts are thin walled-structures located on the peritoneal surface of the uterus, frequently observed as multiple cystic structures in aggregates or grape-like clusters containing a clear, non-viscous fluid. In human and veterinary medicine, they are thought to be developed under hormonal effects, or after manipulation or inflammation of the reproductive tract. However, they have not yet been described in swine. A uterus of a 3-year-old crossbreed sow was condemned at slaughter due to the presence of multiples cystic cavities attached to the serosal surface. Microscopically, multiple cystic dilations emerging from the serosa were lined by a simple and flattened epithelium (cytokeratine positive and vimentin negative on immunohistochemistry) supported by a subepithelial layer of collagen. Grossly and histologically, they were diagnosed as serosal inclusion cysts. To the authors' knowledge, this report represents the first description of serosal inclusion cysts in sows. These lesions should be taken into consideration within the differential diagnostic list of cystic peritoneal lesions such as cystic neoplasms, congenital cysts, and parasitic diseases

Multi-objective multi-scale optimization of composite structures, application to an aircraft overhead locker made with bio-composites

The use of composite materials has grown exponentially in transport structures due to their weight reduction advantages, added to their capability to adapt the material properties and internal micro-structure to the requirements of the application. This flexibility allows the design of highly efficient composite structures that can reduce the environmental impact of transport, especially if the used composites are bio-based. In order to design highly efficient structures, the numerical models and tools used to predict the structural and material performance are of great importance. In the present paper, the authors propose a multi-objective, multi-scale optimization procedure aimed to obtain the best possible structure and material design for a given application. The procedure developed is applied to an aircraft secondary structure, an overhead locker, made with a sandwich laminate in which both, the skins and the core, are bio-materials. The structural multiscale numerical model has been coupled with a Genetic Algorithm to perform the optimization of the structure design. Two optimization cases are presented. The first one consists of a single-objective optimization problem of the fibre alignment to improve the structural stiffness of the structure. The second optimization shows the advantages of using a multi-objective and multi-scale optimization approach. In this last case, the first objective function corresponds to the shelf stiffness, and the second objective function consists of minimizing the number of fibres placed in one of the woven directions, looking for a reduction in the material cost and weight. The obtained results with both optimization cases have proved the capability of the software developed to obtain an optimal design of composite structures, and the need to consider both, the macro-structural and the micro-structural configuration of the composite, in order to obtain the best possible solution. The presented approach allows to perform the optimisation of both the macro-structural and the micro-structural configurations.This work has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 690638, from the Special Research Plan on Civil Aircraft of Ministry for Industry and Information of the People’s Republic of China (MIIT) un- der Grant No MJ-2015-H-G-103, and from the Spanish Ministerio de Economia y Competividad through the project MAT2014-60647-R, Multi-scale and multi-objective optimization of composite laminate structures (OMMC). The authors also acknowledge the Severo Ochoa Centre of Excellence (2019–2023), which financially supported this work under the grant CEX2018-000797-S funded by MCIN/AEI/10.13039/501100011033.Peer ReviewedObjectius de Desenvolupament Sostenible::13 - Acció per al ClimaObjectius de Desenvolupament Sostenible::9 - Indústria, Innovació i InfraestructuraObjectius de Desenvolupament Sostenible::12 - Producció i Consum ResponsablesPostprint (published version