Carlos Henggeler Antunes

113 papers A 4B 14C 8Journal 60Unranked 24

Year	Rank	Type	Title / Venue / Authors
2026	J	`jnl`	Improving the efficiency of logic-based benders decomposition for p-batch scheduling problems with two-dimensional packing. Eur. J. Oper. Res. Paulo Jorge Nascimento, Cristóvão Silva, Carlos Henggeler Antunes, Christos T. Maravelias, Samuel Moniz
2025	—	`conf`	A Genetic Algorithm Approach for Aggregation of Residential Electricity Prosumers' Flexibility. EvoApplications (2) Vahid Rasouli, Álvaro Gomes, Carlos Henggeler Antunes
2024	J	`jnl`	A Novel Three-Phase Multiobjective Unified Power Quality Conditioner. IEEE Trans. Ind. Electron. Vítor Monteiro, Carlos L. Moreira, João Abel Peças Lopes, Carlos Henggeler Antunes, Gerardo J. Osório, João P. S. Catalão, João Luiz Afonso
2024	—	`conf`	An Integrated Optimization-MCDA Framework for Efficient Electric Bus System Planning. ICCAIS Jônatas Augusto Manzolli, João Pedro F. Trovão, Carlos Henggeler Antunes
2024	J	`jnl`	Joint Spectral and Power Efficiency Optimization in Uplink Radio Stripes. IEEE Trans. Commun. Filipe Conceição, Marco Gomes, Vítor Silva, Rui Dinis, Carlos Henggeler Antunes
2024	J	`jnl`	Optimal decomposition approach for solving large nesting and scheduling problems of additive manufacturing systems. Eur. J. Oper. Res. Paulo Jorge Nascimento, Cristóvão Silva, Carlos Henggeler Antunes, Samuel Moniz
2024	J	`jnl`	Special issue on exact and approximation methods for mixed-integer multi-objective optimization. Math. Methods Oper. Res. Carlos Henggeler Antunes, Carlos M. Fonseca, Luís Paquete, Michael Stiglmayr
2023	J	`jnl`	A deterministic bounding algorithm vs. a hybrid meta-heuristic to deal with a bilevel mixed-integer nonlinear optimization model for electricity dynamic pricing. Comput. Oper. Res. Inês Soares, Maria João Alves, Carlos Henggeler Antunes
2023	—	`conf`	Federated Learning Optimization for Energy Communities in Smart Cities. ISC2 Nuno Mendes, Pedro Moura, Jérôme Mendes, Carlos Henggeler Antunes, Javad Mohammadi
2023	—	`conf`	Single and Multi-Objective Bilevel Optimization. GECCO Companion Carlos Henggeler Antunes, Maria João Alves
2022	J	`jnl`	A new exact method for linear bilevel problems with multiple objective functions at the lower level. Eur. J. Oper. Res. Maria João Alves, Carlos Henggeler Antunes
2022	C	`conf`	Dynamic Setpoint Optimization Using Metaheuristic Algorithms for Wastewater Treatment Plants. IECON Rodrigo Salles, Jérôme Mendes, Carlos Henggeler Antunes, Pedro Moura, Joana Dias
2022	C	`conf`	Electric bus smart charging under a bi-level optimisation model to set dynamic tariffs. IECON Jônatas Augusto Manzolli, João Pedro F. Trovão, Carlos Henggeler Antunes
2022	—	`conf`	Hybrid PSO/GA+solver Approaches for a Bilevel Optimization Model to Optimize Electricity Dynamic Tariffs. MIC Maria João Alves, Carlos Henggeler Antunes, Inês Soares
2022	J	`jnl`	Max-Min Fairness Optimization in Uplink Cell-Free Massive MIMO Using Meta-Heuristics. IEEE Trans. Commun. Filipe Conceição, Carlos Henggeler Antunes, Marco Gomes, Vítor Silva, Rui Dinis
2022	—	`conf`	Optimisation of an electric bus charging strategy considering a semi-empirical battery degradation model and weather conditions. ICCAIS Jônatas Augusto Manzolli, João Pedro F. Trovão, Carlos Henggeler Antunes
2022	—	`conf`	Unmanned aerial vehicle positioning and user equipment power allocation. CSNDSP João Martins, Carlos Henggeler Antunes, Marco Gomes, Vítor Silva, Rui Dinis
2022	—	`conf`	User Fairness in Radio Stripes Networks using Meta-Heuristics optimization. VTC Spring Filipe Conceição, Carlos Henggeler Antunes, Marco Gomes, Vítor Silva, Rui Dinis
2021	J	`jnl`	A deterministic bounding procedure for the global optimization of a bi-level mixed-integer problem. Eur. J. Oper. Res. Inês Soares, Maria João Alves, Carlos Henggeler Antunes
2021	J	`jnl`	A population-based approach to the bi-level multifollower problem: an application to the electricity retail market. Int. Trans. Oper. Res. Inês Soares, Maria João Alves, Carlos Henggeler Antunes
2021	J	`jnl`	Modelling state spaces and discrete control using MILP: computational cost considerations for demand response. EAI Endorsed Trans. Energy Web Pedro M. L. P. Magalhães, Carlos Henggeler Antunes
2021	J	`jnl`	New concepts and an algorithm for multiobjective bilevel programming: optimistic, pessimistic and moderate solutions. Oper. Res. Maria João Alves, Carlos Henggeler Antunes, João Paulo Costa
2020	B	`conf`	Optimizing Prices and Periods in Time-of-use Electricity Tariff Design Using Bilevel Programming. EvoCOP Maria João Alves, Carlos Henggeler Antunes, Inês Soares
2020	J	`jnl`	Sizing of a Battery Pack Based on Series/Parallel Configurations for a High-Power Electric Vehicle as a Constrained Optimization Problem. IEEE Trans. Veh. Technol. Louis Pelletier, Félix-Antoine LeBel, Carlos Henggeler Antunes, João Pedro F. Trovão
2019	B	`conf`	A Hybrid Multiobjective Differential Evolution Approach to Stator Winding Optimization. EvoApplications André M. Silva, Fernando J. T. E. Ferreira, Carlos Henggeler Antunes
2019	—	`conf`	A bi-level hybrid PSO: MIP solver approach to define dynamic tariffs and estimate bounds for an electricity retailer profit. GECCO (Companion) Inês Soares, Maria João Alves, Carlos Henggeler Antunes
2019	—	`conf`	Comparison of Thermal Load Models for MILP-Based Demand Response Planning. SESC Pedro M. L. P. Magalhães, Carlos Henggeler Antunes
2019	—	`conf`	Optimization of PMU Location and Communications in a Power Grid. RNDM Luís Alçada-Almeida, Teresa Gomes, Carlos Henggeler Antunes
2018	J	`jnl`	A Controllable Bidirectional Battery Charger for Electric Vehicles with Vehicle-to-Grid Capability. IEEE Trans. Veh. Technol. Hugo Neves de Melo, João Pedro F. Trovão, Paulo G. Pereirinha, Humberto M. Jorge, Carlos Henggeler Antunes
2018	J	`jnl`	A semivectorial bilevel programming approach to optimize electricity dynamic time-of-use retail pricing. Comput. Oper. Res. Maria João Alves, Carlos Henggeler Antunes
2018	—	`conf`	Energy End-Use Flexibility of the Next Generation of Decision-Makers in a Smart Grid Setting: An Exploratory Study. GreeNets Inês F. G. Reis, Marta A. R. Lopes, Paula F. V. Ferreira, Carlos Henggeler Antunes, Madalena Araújo
2018	J	`jnl`	Integrated Management of Energy Resources in Residential Buildings - A Markovian Approach. IEEE Trans. Smart Grid Maricica Nistor, Carlos Henggeler Antunes
2018	A	`conf`	Optimizing residential energy resources with an improved multi-objective genetic algorithm based on greedy mutations. GECCO Ivo Gonçalves, Álvaro Gomes, Carlos Henggeler Antunes
2018	J	`jnl`	Performance evaluation of Portuguese mutual fund portfolios using the value-based DEA method. J. Oper. Res. Soc. Maria do Castelo Gouveia, Elisabete Duarte Neves, Luís Cândido Dias, Carlos Henggeler Antunes
2017	J	`jnl`	A Customized Evolutionary Algorithm for Multiobjective Management of Residential Energy Resources. IEEE Trans. Ind. Informatics Ana Soares, Álvaro Gomes, Carlos Henggeler Antunes, Carlos Oliveira
2017	—	`conf`	A Differential Evolution Algorithm to Semivectorial Bilevel Problems. MOD Maria João Alves, Carlos Henggeler Antunes
2017	J	`jnl`	Bi-level particle swarm optimization and evolutionary algorithm approaches for residential demand response with different user profiles. Inf. Sci. Pedro Carrasqueira, Maria João Alves, Carlos Henggeler Antunes
2016	—	`conf`	A Hybrid Genetic Algorithm for the Interaction of Electricity Retailers with Demand Response. EvoApplications (1) Maria João Alves, Carlos Henggeler Antunes, Pedro Carrasqueira
2016	J	`jnl`	An application of value-based DEA to identify the best practices in primary health care. OR Spectr. Maria do Castelo Gouveia, Luis C. Dias, Carlos Henggeler Antunes, M. A. Mota, E. M. Duarte, E. M. Tenreiro
2016	—	`conf`	An illustration of different concepts of solutions in semivectorial bilevel programming. SSCI Maria João Alves, Carlos Henggeler Antunes
2016	—	`conf`	Assessing the robustness of solutions to a multi-objective model of an energy management system aggregator. SSCI Andreia M. Carreiro, Carlos Henggeler Antunes, Humberto Jorge
2016	—	`conf`	Beamforming Optimization for Multiuser Wireless Systems Using Meta-Heuristics. VTC Fall Pedro Bento, Carlos Henggeler Antunes, Marco Alexandre Cravo Gomes, Rui Dinis, Vítor Manuel Mendes da Silva
2016	J	`jnl`	Coupling input-output analysis with multiobjective linear programming models for the study of economy-energy-environment-social (E3S) trade-offs: a review. Ann. Oper. Res. Carlos Oliveira, Dulce Helena Carvalho Coelho, Carlos Henggeler Antunes
2016	J	`jnl`	Effectiveness of Supercapacitors in Pure Electric Vehicles Using a Hybrid Metaheuristic Approach. IEEE Trans. Veh. Technol. Felipe Machado, João Pedro F. Trovão, Carlos Henggeler Antunes
2016	B	`conf`	Sensor location in water distribution networks to detect contamination events - A multiobjective approach based on NSGA-II. CEC Carlos Henggeler Antunes, Dolores Margarida
2016	C	`conf`	Single and Multiple Objective Optimization Models for Opportunistic Preventive Maintenance. ICORES Carlos Henggeler Antunes, Maria João Alves, Joana Dias, Teresa Gomes, Benjamim Cardoso, José Freitas
2015	—	`conf`	A Bi-level Multiobjective PSO Algorithm. EMO (1) Pedro Carrasqueira, Maria João Alves, Carlos Henggeler Antunes
2015	A	`conf`	A PSO Approach to Semivectorial Bilevel Programming: Pessimistic, Optimistic and Deceiving Solutions. GECCO Maria João Alves, Carlos Henggeler Antunes, Pedro Carrasqueira
2015	J	`jnl`	A Real-Time Energy Management Architecture for Multisource Electric Vehicles. IEEE Trans. Ind. Electron. João Pedro F. Trovão, Victor D. N. Santos, Carlos Henggeler Antunes, Paulo G. Pereirinha, Humberto M. Jorge
2015	B	`conf`	An Energy Management System Aggregator Based on an Integrated Evolutionary and Differential Evolution Approach. EvoApplications Andreia M. Carreiro, Carlos Oliveira, Carlos Henggeler Antunes, Humberto M. Jorge
2015	—	`ed.`	Evolutionary Multi-Criterion Optimization - 8th International Conference, EMO 2015, Guimarães, Portugal, March 29 -April 1, 2015. Proceedings, Part I EMO (1) António Gaspar-Cunha, Carlos Henggeler Antunes, Carlos A. Coello Coello
2015	—	`ed.`	Evolutionary Multi-Criterion Optimization - 8th International Conference, EMO 2015, Guimarães, Portugal, March 29 -April 1, 2015. Proceedings, Part II EMO (2) António Gaspar-Cunha, Carlos Henggeler Antunes, Carlos A. Coello Coello
2015	J	`jnl`	GerAPlanO - A new building design tool: design generation, thermal assessment and performance optimization. CoRR Eugénio Rodrigues, Ana Rita Amaral, Adélio Rodrigues Gaspar, Álvaro Gomes, Manuel Carlos Gameiro da Silva, Carlos Henggeler Antunes
2015	J	`jnl`	Interactive MOLP explorer - A graphical-based computational tool for teaching and decision support in multi-objective linear programming models. Comput. Appl. Eng. Educ. Maria João Alves, Carlos Henggeler Antunes, João C. N. Clímaco
2015	—	`conf`	Multi-objective Optimization of Sensor Placement to Detect Contamination in Water Distribution Networks. GECCO (Companion) Dolores Margarida, Carlos Henggeler Antunes
2015	J	`jnl`	Online survey for collective clustering of computer generated architectural floor plans. CoRR David Sousa-Rodrigues, Mafalda Teixeira de Sampayo, Eugénio Rodrigues, Adélio Rodrigues Gaspar, Álvaro Gomes, Carlos Henggeler Antunes
2014	—	`conf`	A hybrid multi-objective GRASP+SA algorithm with incorporation of preferences. MCDM Eunice Oliveira, Carlos Henggeler Antunes, Álvaro Gomes
2014	B	`conf`	An Improved Multiobjective Electromagnetism-like Mechanism Algorithm. EvoApplications Pedro Carrasqueira, Maria João Alves, Carlos Henggeler Antunes
2014	—	`conf`	An Optimization Model for the Aggregation of End-user Energy Management Systems in a Residential Setting. SMARTGREENS Andreia M. Carreiro, Carlos Henggeler Antunes, Humberto M. Jorge
2014	—	`conf`	Automatic Clustering Using a Genetic Algorithm with New Solution Encoding and Operators. ICCSA (2) Carolina Raposo, Carlos Henggeler Antunes, João Pedro Barreto
2014	J	`jnl`	Learning of a single-hidden layer feedforward neural network using an optimized extreme learning machine. Neurocomputing Tiago Matias, Francisco Souza, Rui Araújo, Carlos Henggeler Antunes
2014	J	`jnl`	Uncertainty and robustness in planning and decision-making. Int. J. Syst. Sci. Carlos Henggeler Antunes, David Ríos Insua, Luís Cândido Dias
2013	J	`jnl`	A comparative study of different approaches using an outranking relation in a multi-objective evolutionary algorithm. Comput. Oper. Res. Eunice Oliveira, Carlos Henggeler Antunes, Álvaro Gomes
2013	—	`conf`	A hybrid evolutionary simulated annealing algorithm with incorporation of preferences. GECCO (Companion) Eunice Oliveira, Carlos Henggeler Antunes, Álvaro Gomes
2013	C	`conf`	A unified energy management strategy for a dual-source electric vehicle. IECON João Pedro F. Trovão, Victor D. N. Santos, Paulo G. Pereirinha, Humberto M. Jorge, Carlos Henggeler Antunes
2013	J	`jnl`	Comparison of a genetic algorithm and simulated annealing for automatic neural network ensemble development. Neurocomputing Symone G. Soares, Carlos Henggeler Antunes, Rui Araújo
2013	C	`conf`	DC-link stability control for dual-source electric vehicles using an extended kalman filter. IECON Felipe Machado, João Pedro F. Trovão, Carlos Henggeler Antunes
2013	B	`conf`	Domestic Load Scheduling Using Genetic Algorithms. EvoApplications Ana Soares, Álvaro Gomes, Carlos Henggeler Antunes, Hugo Cardoso
2013	C	`conf`	Genetically optimized extreme learning machine. ETFA Tiago Matias, Rui Araújo, Carlos Henggeler Antunes, Dulce Gabriel
2013	J	`jnl`	Super-efficiency and stability intervals in additive DEA. J. Oper. Res. Soc. Maria do Castelo Gouveia, Luis C. Dias, Carlos Henggeler Antunes
2012	C	`conf`	A Multi-criteria Sorting Approach for Diagnosing Mental Disabilities. ICORES Paulo Freitas, Carlos Henggeler Antunes, Jorge Dias
2012	A	`conf`	A genetic algorithm for designing neural network ensembles. GECCO Symone G. Soares, Carlos Henggeler Antunes, Rui Araújo
2012	J	`jnl`	Dealing with uncertainty in Decision Support Systems: Recent trends (2000-2011). Intell. Decis. Technol. Luis C. Dias, Carlos Henggeler Antunes, David Ríos Insua
2012	J	`jnl`	Special issue on intelligent technologies for planning and decision making under uncertainty. Intell. Decis. Technol. Luís Cândido Dias, Carlos Henggeler Antunes, David Ríos Insua
2011	J	`jnl`	A GIS-based multicriteria spatial decision support system for planning urban infrastructures. Decis. Support Syst. João Manuel Coutinho-Rodrigues, Ana Simão, Carlos Henggeler Antunes
2011	J	`jnl`	A web spatial decision support system for vehicle routing using Google Maps. Decis. Support Syst. Luís Santos, João Manuel Coutinho-Rodrigues, Carlos Henggeler Antunes
2011	A	`conf`	Adaptive and hybrid genetic approaches for estimating the camera motion from image point correspondences. GECCO Francisco Vasconcelos, Carlos Henggeler Antunes, João Pedro Barreto
2011	J	`jnl`	Incorporation of Preferences in an Evolutionary Algorithm Using an Outranking Relation: The EvABOR Approach. Int. J. Nat. Comput. Res. Eunice Oliveira, Carlos Henggeler Antunes, Álvaro Gomes
2010	B	`conf`	A study of genetic algorithms for approximating the longest path in generic graphs. SMC David Portugal, Carlos Henggeler Antunes, Rui P. Rocha
2010	B	`conf`	An Evolutionary Algorithm Guided by Preferences Elicited According to the ELECTRE TRI Method Principles. EvoCOP Eunice Oliveira, Carlos Henggeler Antunes
2010	B	`conf`	An Evolutionary Algorithm based on an outranking relation for sorting problems. SMC Eunice Oliveira, Carlos Henggeler Antunes
2010	J	`jnl`	Improving the responsiveness of NSGA-II using an adaptive mutation operator: a case study. Int. J. Adv. Intell. Paradigms Álvaro Gomes, Carlos Henggeler Antunes, Antonio Gomes Martins
2010	B	`conf`	Reconstruction of the non-minimum phase response of chirped fiber Bragg gratings using an adaptive genetic algorithm. IEEE Congress on Evolutionary Computation Filipe M. Ferreira, Paulo E. M. de Almeida, Carlos Henggeler Antunes, Henrique J. A. da Silva
2009	J	`jnl`	Assessing the performance of biogas plants with multi-criteria and data envelopment analysis. Eur. J. Oper. Res. Reinhard Madlener, Carlos Henggeler Antunes, Luis C. Dias
2009	J	`jnl`	Operational research models and methods in the energy sector. Eur. J. Oper. Res. Carlos Henggeler Antunes, Álvaro Gomes
2009	B	`conf`	Robustness Analysis in Evolutionary Multi-Objective Optimization Applied to VAR Planning in Electrical Distribution Networks. EvoCOP Carlos Barrico, Carlos Henggeler Antunes, Dulce Fernão Pires
2009	J	`jnl`	Structuring an MCDA model using SSM: A case study in energy efficiency. Eur. J. Oper. Res. L. P. Neves, Luis C. Dias, Carlos Henggeler Antunes, Antonio Gomes Martins
2009	C	`conf`	Using Attainment Surface for Comparing NSGA-II and SPEA-II - A Case Study. IJCCI Álvaro Gomes, Carlos Henggeler Antunes, Antonio Gomes Martins, João Melo
2008	J	`jnl`	Additive DEA based on MCDA with imprecise information. J. Oper. Res. Soc. Maria do Castelo Gouveia, Luis C. Dias, Carlos Henggeler Antunes
2008	J	`jnl`	Design of an adaptive mutation operator in an electrical load management case study. Comput. Oper. Res. Álvaro Gomes, Carlos Henggeler Antunes, Antonio Gomes Martins
2008	—	`conf`	Improving the Responsiveness of NSGA-II in Dynamic Environments Using an Adaptive Mutation Operator - A Case Study. KES (1) Álvaro Gomes, Carlos Henggeler Antunes, Antonio Gomes Martins
2008	J	`jnl`	Stability analysis of efficient solutions in multiobjective integer programming: A case study in load management. Comput. Oper. Res. Maria João Alves, João C. N. Clímaco, Carlos Henggeler Antunes, Humberto Jorge, Antonio Gomes Martins
2007	J	`jnl`	A multicriteria decision support system for housing evaluation. Decis. Support Syst. Eduardo Natividade-Jesus, João Manuel Coutinho-Rodrigues, Carlos Henggeler Antunes
2007	—	`ch.`	An Evolutionary Approach for Assessing the Degree of Robustness of Solutions to Multi-Objective Models. Evolutionary Computation in Dynamic and Uncertain Environments Carlos Barrico, Carlos Henggeler Antunes
2007	J	`jnl`	Managing uncertainty in decision support models foreword to the special issue. Decis. Support Syst. Carlos Henggeler Antunes, Luis C. Dias
2007	J	`jnl`	Managing uncertainty in decision support models. Eur. J. Oper. Res. Carlos Henggeler Antunes, Luis C. Dias
2007	J	`jnl`	Multiple objective linear programming models with interval coefficients - an illustrated overview. Eur. J. Oper. Res. Carla Oliveira Henriques, Carlos Henggeler Antunes
2007	B	`conf`	Stability analysis of multiple objective linear programming models to the introduction of new decision variables. SMC Ana Rosa Pereira Borges, Carlos Henggeler Antunes
2006	J	`jnl`	International Series in Operations Research and Management Science, William W. Cooper, Lawrence M. Seiford, Joe Zhu. Kluwer Academic Publishers (2004), ISBN: 1-4020-7797-1. Eur. J. Oper. Res. Carlos Henggeler Antunes
2006	J	`jnl`	Multiobjective optimisation and control, G.P. Liu, J.B. Yang, J.F. Whidborne, in: Series: Engineering Systems Modelling and Control. Research Studies Press (2003), ISBN: 0 86380 264 8. Eur. J. Oper. Res. Carlos Henggeler Antunes
2006	B	`conf`	Robustness Analysis in Multi-Objective Optimization Using a Degree of Robustness Concept. IEEE Congress on Evolutionary Computation Carlos Barrico, Carlos Henggeler Antunes
2004	J	`jnl`	A multiple objective model to deal with economy-energy-environment interactions. Eur. J. Oper. Res. Carla Oliveira Henriques, Carlos Henggeler Antunes
2004	B	`conf`	Dealing with Solution Diversity in an EA for Multiple Objective Decision Support - A Case Study. EvoCOP Álvaro Gomes, Carlos Henggeler Antunes, Antonio Gomes Martins
2004	J	`jnl`	Using SSM to rethink the analysis of energy efficiency initiatives. J. Oper. Res. Soc. L. M. P. Neves, Antonio Gomes Martins, Carlos Henggeler Antunes, Luis C. Dias
2003	J	`jnl`	A fuzzy multiple objective decision support model for energy-economy planning. Eur. J. Oper. Res. Ana Rosa Pereira Borges, Carlos Henggeler Antunes
2003	J	`jnl`	A weight space-based approach to fuzzy multiple-objective linear programming. Decis. Support Syst. Ana Rosa Pereira Borges, Carlos Henggeler Antunes
2003	J	`jnl`	Preface. Ann. Oper. Res. Carlos Henggeler Antunes, Antonio Gomes Martins
2002	J	`jnl`	A visual interactive tolerance approach to sensitivity analysis in MOLP. Eur. J. Oper. Res. Ana Rosa Pereira Borges, Carlos Henggeler Antunes
1998	J	`jnl`	Planning the evolution to broadband access networks: A multicriteria approach. Eur. J. Oper. Res. Carlos Henggeler Antunes, José M. F. Craveirinha, João C. N. Clímaco
1994	J	`jnl`	A decision support system dedicated to discrete multiple criteria problems. Decis. Support Syst. Carlos Henggeler Antunes, Luís Alçada-Almeida, Virgínia Lopes, João C. N. Clímaco
1994	J	`jnl`	On the application of TRIMAP to problems with multiple decision makers. Ann. Oper. Res. João C. N. Clímaco, Carlos Henggeler Antunes
1992	J	`jnl`	An integrated MOLP method base package - A guided tour of tommix. Comput. Oper. Res. Carlos Henggeler Antunes, Maria João Alves, Ana L. Silva, João C. N. Clímaco
1992	J	`jnl`	Sensitivity analysis in MCDM using the weight space. Oper. Res. Lett. Carlos Henggeler Antunes, João C. N. Clímaco