In order to minimize execution times, improve the quality of solutions, and address more extensiv... more In order to minimize execution times, improve the quality of solutions, and address more extensive target situations, optimization techniques, particularly metaheuristics, are continually improved. Hybridizing procedures are one of these noteworthy strategies due to their wide range of applications. This article describes a hybrid algorithm that combines the k-means method to produce a binary version of the cuckoo search and sine cosine algorithms. The binary algorithms are applied on the NP-hard multi-demand multidimensional knapsack problem. This problem is of particular interest because it has two types of constraints. The first group of constraints is related to the capacity of the knapsacks, and a second type is associated with the demand that must be met. Experiments were undertaken to acquire insight into the contribution of the k-means technique and the local search operator to the final results. Additionally, a comparison is made with two other types of binarization, the fi...
Acknowledging the possible impacts of the location of a vertical handrail on the accessibility of... more Acknowledging the possible impacts of the location of a vertical handrail on the accessibility of wheelchair passengers, this study explores different dimensions of the vertical handrail and elements of the internal space of a metro carriage and how they can impact the behaviour of passengers. For this purpose, simulation scenarios have been developed with different configurations of the location of the vertical handrail, which includes variables such as the number of passengers boarding and alighting and the type of relationship that exists between them. In this way, participants have been recruited for the simulation in a controlled environment, using a mock-up with characteristics and dimensions representing the space inside a metro carriage. The results show that the current location, that is, in the centre of the carriage, affects the accessibility of wheelchair users. Similarly, it has been observed that placing the handrail on one side of the train has positive effects on the...
2019 6th International Conference on Systems and Informatics (ICSAI)
Combinatorial problems with NP-hard complexity appear frequently in operational research. Making ... more Combinatorial problems with NP-hard complexity appear frequently in operational research. Making robust algorithms that solve these combinatorial problems is of interest in operational research. In this article, a binarization mechanism is proposed so that continuous metaheuristics can solve combinatorial problems. The binarization mechanism uses the concept of percentile. This percentile mechanism is applied to the ant lion algorithm. The NP-hard knapsack problem (MKP) was used to verify our algorithm. Additionally, the binary percentile algorithm was compared with other algorithms that have recently has solved the MKP, observing that the percentile algorithm produces competitive results.
During last 5 years, the Ministry of Public Works and the Pontificia Universidad Católica de Valp... more During last 5 years, the Ministry of Public Works and the Pontificia Universidad Católica de Valparaíso are developing a Risk Management System applied in several road infrastructures called GRDR. This methodology is focus on the inspection on: 1. Structures in order to identify the vulnerability; 2. environmental conditions with the aim to identify the exposure and hazard. The relations between these indexes use an algorithm to apply the weight on the parameters. Currently, the deterministics inspection use a comprehensive management program provides an index of vulnerability (Performance indicators) in structures as bridges and pavements. But it is not included the hazard or exposure index. This paper delivers the first index of hazards and exposure related with seismic, flooding and fire threat applied on the Risk Management System (GRDR), with an implementation on two main Chilean structures, namely: La Pólvora Tunnel T3, a medium long span structure, located at the Region Valpa...
Artificial Intelligence in Intelligent Systems, 2021
In the fields of engineering and science, there are many combinatorial optimization problems. Man... more In the fields of engineering and science, there are many combinatorial optimization problems. Many of these problems are NP-hard problems, which are difficult to solve with complete techniques. Therefore, the design of binary algorithms based on swarm intelligence continuous metaheuristics is an area of interest in operations research. In this article, we use a general binarization mechanism based on the k-means technique. We apply k-means technique to the firefly algorithm to solve the multidimensional knapsack problem (MKP). Design experiments to prove the practicality of k-means technique in binarization.
Artificial Intelligence in Intelligent Systems, 2021
The application of continuous metaheuristic algorithms to combinatorial problems is an area of in... more The application of continuous metaheuristic algorithms to combinatorial problems is an area of interest at the engineering level. This interest is related to the fact that many of the problems that are addressed at the industrial level are of the combinatorial type and a not lesser subset of these are of the NP-hard type. In this article, we propose a binarization mechanism for continuous metaheuristics that uses the concept of percentile. This percentile concept is applied to the firefly optimization algorithm to solve the set covering problem (SCP). To determine the importance of the percentile concept, experiments were designed to identify its contribution. Additionally, to see that the proposal is adequate, the efficiency of the algorithm is compared using reference instances. The results indicate that the binary percentile firefly algorithm (BPFA) obtains adequate results when evaluated with a combinatorial problem such as the SCP.
Optimization techniques, specially metaheuristics, are constantly refined in order to decrease ex... more Optimization techniques, specially metaheuristics, are constantly refined in order to decrease execution times, increase the quality of solutions, and address larger target cases. Hybridizing techniques are one of these strategies that are particularly noteworthy due to the breadth of applications. In this article, a hybrid algorithm is proposed that integrates the k-means algorithm to generate a binary version of the cuckoo search technique, and this is strengthened by a local search operator. The binary cuckoo search algorithm is applied to the NP-hard Set-Union Knapsack Problem. This problem has recently attracted great attention from the operational research community due to the breadth of its applications and the difficulty it presents in solving medium and large instances. Numerical experiments were conducted to gain insight into the contribution of the final results of the k-means technique and the local search operator. Furthermore, a comparison to state-of-the-art algorithm...
This article proposes a hybrid algorithm that makes use of the db-scan unsupervised learning tech... more This article proposes a hybrid algorithm that makes use of the db-scan unsupervised learning technique to obtain binary versions of continuous swarm intelligence algorithms. These binary versions are then applied to large instances of the well-known multidimensional knapsack problem. The contribution of the db-scan operator to the binarization process is systematically studied. For this, two random operators are built that serve as a baseline for comparison. Once the contribution is established, the db-scan operator is compared with two other binarization methods that have satisfactorily solved the multidimensional knapsack problem. The first method uses the unsupervised learning technique k-means as a binarization method. The second makes use of transfer functions as a mechanism to generate binary versions. The results show that the hybrid algorithm using db-scan produces more consistent results compared to transfer function (TF) and random operators.
Journal of Information Systems Engineering & Management, 2019
The binarization mechanisms of continuous metaheuristics are of interest in operational research.... more The binarization mechanisms of continuous metaheuristics are of interest in operational research. This is mainly due to the fact that there are a lot of combinatorial problems that are NP-hard. In this article, we exploit the concept of percentile as a mechanism of binarization of swarm intelligence continuous metaheuristics. To evaluate the behavior of our binary operator, the Multi-verse metaheuristic is used and applied to solve the combinatorial problem of the knapsack. The binary algorithm obtained, the binary multi-verse Optimizer (BMVO) shows good performance in solving the most difficult problems of the knapsack.
The integration of machine learning techniques and metaheuristic algorithms is an area of interes... more The integration of machine learning techniques and metaheuristic algorithms is an area of interest due to the great potential for applications. In particular, using these hybrid techniques to solve combinatorial optimization problems (COPs) to improve the quality of the solutions and convergence times is of great interest in operations research. In this article, the db-scan unsupervised learning technique is explored with the goal of using it in the binarization process of continuous swarm intelligence metaheuristic algorithms. The contribution of the db-scan operator to the binarization process is analyzed systematically through the design of random operators. Additionally, the behavior of this algorithm is studied and compared with other binarization methods based on clusters and transfer functions (TFs). To verify the results, the well-known set covering problem is addressed, and a real-world problem is solved. The results show that the integration of the db-scan technique produc...
Fatigue & Fracture of Engineering Materials & Structures, 2017
Open-cell aluminium foams are a relatively new material with interesting uses in different engine... more Open-cell aluminium foams are a relatively new material with interesting uses in different engineering applications. This study investigates the fatigue behaviour and damage accumulation of metal foams via a fatigue analysis (Weibull E-N model), a failure criterion (the relation among the prepeak compressive and tensile slopes, the reduction in the tensile stress, or the reduction in the compressive stress), and a mathematical approach (linear, quadratic, or exponential). As a result of combining the 3 mathematical approaches and 3 failure criteria, different approaches are obtained, analysed, and validated by using experimental data. Finally, the proposed approaches can be used to directly obtain the damage accumulation level for open-cell metal foams under fully reversed cyclic loading as a function of the number of cycles applied, the total strain amplitude, and the initial damage accumulation condition.
Objective: This study was conducted to establish associations among the Candida carriage rate, th... more Objective: This study was conducted to establish associations among the Candida carriage rate, the diversity of Candida species carried and the different caries status of preschool children. Materials and methods: Sixty-one children between 2 and 5 years of age were examined by a single expert examiner and were divided into three groups, the caries-free, moderate caries and severe caries groups, according to the criteria of the International Caries Detection and Assessment System II (ICDAS). Saliva samples were obtained from the members of each group and were plated on Sabouraud agar plates to assess the Candida carriage rates. CHROMagar Candida medium was used for the preliminary screening. Biochemical testing or PCR/sequencing was conducted to identify the different Candida species in the samples. The differences observed were considered significant if the p value was <0.05. Results: The Candida carriage rate and the number of species of this fungus carried were higher in the group with the highest level of caries severity (p < 0.05). Whereas Candida albicans was the most predominant Candida species in the saliva of all of the children, C. dubliniensis was identified only in the most caries-affected group in addition to other rare species of Candida non-albicans. Conclusions: A high salivary Candida carriage rate and the presence of specific species of this fungus (such as C. albicans and C. dubliniensis) appear to be related to the severity of caries experienced by preschool children.
Computer-Aided Civil and Infrastructure Engineering, 2016
Existing computer models used to optimize railway timetables lead to a high complexity when the n... more Existing computer models used to optimize railway timetables lead to a high complexity when the number of analyzed services exceeds a given threshold. A time partitioning technique is proposed which allows line design and timetable optimization and a reduction in the complexity of the problem by considering small time windows of the same or different durations in which the timetables of a small (equal or not) number of running trains are optimized in sequence. Though the optimal solution is not expected to be attained with this method, the analyzed examples demonstrate that the resulting solution is close to the global optimum and practically satisfactory. This technique can be used at the planning and implementation stages. Examples of two real lines are analyzed to show the goodness of the proposed methods. One is the network Madrid-Sevilla-Toledo-Málaga-Valencia-Albacete with a dense traffic of 170 trains per day. The second is the Palencia-Santander
Artemia franciscana es uno de los organismos vivos más utilizados para la alimentación de especie... more Artemia franciscana es uno de los organismos vivos más utilizados para la alimentación de especies en cultivo, debido a que presenta varias proteínas y ácidos grasos insaturados que juegan un rol fundamental en diversas funciones metabólicas de las especies cultivadas. Esta especie corresponde a un crustáceo pequeño branquiópodo, filtrador no selectivo, propio de hábitats acuáticos de elevada salinidad. En la etapa adulta pueden ser especies bisexuales y partenogenéticas, en ambas poblaciones las hembras pueden dar lugar a dos tipos de reproducción, ovovivípara que resulta en un nauplio completamente formado; y ovípara que resulta un cistos que pueden dar una eclosión inmediata o entrar en estado criptobiótico o de diapausa por largos períodos, facilitando la obtención de nauplios durante todo el año. Con el objetivo de establecer las variables de salinidad y temperatura óptimas para la reproducción ovípara y posterior desarrollo de Artemia franciscana, en la zona norte de Chile, se realizó un cultivo experimental con adultos reproductores, los que fueron sometidos a nueve tratamientos con tres réplicas, a diferentes rangos de salinidad (100 g/L, 120 g/L y 140 g/L) y temperatura (20 °C, 25 °C y 30 °C), donde los cistos obtenidos se colectaron diariamente y se almacenaron durante dos semanas para después determinar la calidad de estos sobre la base del porcentaje y eficiencia de eclosión, aplicándose a los datos obtenidos un análisis de varianza de dos vías (ANOVA) para establecer diferencias significativas entre los tratamientos. Los resultados del análisis establecieron que existe diferencia significativa entre la salinidad y temperatura de experimentación, debido a que por separado solamente la salinidad presenta una incidencia en la reproducción. Se pone de manifiesto que los parámetros fisicoquímicos adecuados para reproducción ovípara de A. franciscana es de 120 g/L a 25 °C, debido a que presenta una diferencia significativa al nivel p < 0,054.
In order to minimize execution times, improve the quality of solutions, and address more extensiv... more In order to minimize execution times, improve the quality of solutions, and address more extensive target situations, optimization techniques, particularly metaheuristics, are continually improved. Hybridizing procedures are one of these noteworthy strategies due to their wide range of applications. This article describes a hybrid algorithm that combines the k-means method to produce a binary version of the cuckoo search and sine cosine algorithms. The binary algorithms are applied on the NP-hard multi-demand multidimensional knapsack problem. This problem is of particular interest because it has two types of constraints. The first group of constraints is related to the capacity of the knapsacks, and a second type is associated with the demand that must be met. Experiments were undertaken to acquire insight into the contribution of the k-means technique and the local search operator to the final results. Additionally, a comparison is made with two other types of binarization, the fi...
Acknowledging the possible impacts of the location of a vertical handrail on the accessibility of... more Acknowledging the possible impacts of the location of a vertical handrail on the accessibility of wheelchair passengers, this study explores different dimensions of the vertical handrail and elements of the internal space of a metro carriage and how they can impact the behaviour of passengers. For this purpose, simulation scenarios have been developed with different configurations of the location of the vertical handrail, which includes variables such as the number of passengers boarding and alighting and the type of relationship that exists between them. In this way, participants have been recruited for the simulation in a controlled environment, using a mock-up with characteristics and dimensions representing the space inside a metro carriage. The results show that the current location, that is, in the centre of the carriage, affects the accessibility of wheelchair users. Similarly, it has been observed that placing the handrail on one side of the train has positive effects on the...
2019 6th International Conference on Systems and Informatics (ICSAI)
Combinatorial problems with NP-hard complexity appear frequently in operational research. Making ... more Combinatorial problems with NP-hard complexity appear frequently in operational research. Making robust algorithms that solve these combinatorial problems is of interest in operational research. In this article, a binarization mechanism is proposed so that continuous metaheuristics can solve combinatorial problems. The binarization mechanism uses the concept of percentile. This percentile mechanism is applied to the ant lion algorithm. The NP-hard knapsack problem (MKP) was used to verify our algorithm. Additionally, the binary percentile algorithm was compared with other algorithms that have recently has solved the MKP, observing that the percentile algorithm produces competitive results.
During last 5 years, the Ministry of Public Works and the Pontificia Universidad Católica de Valp... more During last 5 years, the Ministry of Public Works and the Pontificia Universidad Católica de Valparaíso are developing a Risk Management System applied in several road infrastructures called GRDR. This methodology is focus on the inspection on: 1. Structures in order to identify the vulnerability; 2. environmental conditions with the aim to identify the exposure and hazard. The relations between these indexes use an algorithm to apply the weight on the parameters. Currently, the deterministics inspection use a comprehensive management program provides an index of vulnerability (Performance indicators) in structures as bridges and pavements. But it is not included the hazard or exposure index. This paper delivers the first index of hazards and exposure related with seismic, flooding and fire threat applied on the Risk Management System (GRDR), with an implementation on two main Chilean structures, namely: La Pólvora Tunnel T3, a medium long span structure, located at the Region Valpa...
Artificial Intelligence in Intelligent Systems, 2021
In the fields of engineering and science, there are many combinatorial optimization problems. Man... more In the fields of engineering and science, there are many combinatorial optimization problems. Many of these problems are NP-hard problems, which are difficult to solve with complete techniques. Therefore, the design of binary algorithms based on swarm intelligence continuous metaheuristics is an area of interest in operations research. In this article, we use a general binarization mechanism based on the k-means technique. We apply k-means technique to the firefly algorithm to solve the multidimensional knapsack problem (MKP). Design experiments to prove the practicality of k-means technique in binarization.
Artificial Intelligence in Intelligent Systems, 2021
The application of continuous metaheuristic algorithms to combinatorial problems is an area of in... more The application of continuous metaheuristic algorithms to combinatorial problems is an area of interest at the engineering level. This interest is related to the fact that many of the problems that are addressed at the industrial level are of the combinatorial type and a not lesser subset of these are of the NP-hard type. In this article, we propose a binarization mechanism for continuous metaheuristics that uses the concept of percentile. This percentile concept is applied to the firefly optimization algorithm to solve the set covering problem (SCP). To determine the importance of the percentile concept, experiments were designed to identify its contribution. Additionally, to see that the proposal is adequate, the efficiency of the algorithm is compared using reference instances. The results indicate that the binary percentile firefly algorithm (BPFA) obtains adequate results when evaluated with a combinatorial problem such as the SCP.
Optimization techniques, specially metaheuristics, are constantly refined in order to decrease ex... more Optimization techniques, specially metaheuristics, are constantly refined in order to decrease execution times, increase the quality of solutions, and address larger target cases. Hybridizing techniques are one of these strategies that are particularly noteworthy due to the breadth of applications. In this article, a hybrid algorithm is proposed that integrates the k-means algorithm to generate a binary version of the cuckoo search technique, and this is strengthened by a local search operator. The binary cuckoo search algorithm is applied to the NP-hard Set-Union Knapsack Problem. This problem has recently attracted great attention from the operational research community due to the breadth of its applications and the difficulty it presents in solving medium and large instances. Numerical experiments were conducted to gain insight into the contribution of the final results of the k-means technique and the local search operator. Furthermore, a comparison to state-of-the-art algorithm...
This article proposes a hybrid algorithm that makes use of the db-scan unsupervised learning tech... more This article proposes a hybrid algorithm that makes use of the db-scan unsupervised learning technique to obtain binary versions of continuous swarm intelligence algorithms. These binary versions are then applied to large instances of the well-known multidimensional knapsack problem. The contribution of the db-scan operator to the binarization process is systematically studied. For this, two random operators are built that serve as a baseline for comparison. Once the contribution is established, the db-scan operator is compared with two other binarization methods that have satisfactorily solved the multidimensional knapsack problem. The first method uses the unsupervised learning technique k-means as a binarization method. The second makes use of transfer functions as a mechanism to generate binary versions. The results show that the hybrid algorithm using db-scan produces more consistent results compared to transfer function (TF) and random operators.
Journal of Information Systems Engineering & Management, 2019
The binarization mechanisms of continuous metaheuristics are of interest in operational research.... more The binarization mechanisms of continuous metaheuristics are of interest in operational research. This is mainly due to the fact that there are a lot of combinatorial problems that are NP-hard. In this article, we exploit the concept of percentile as a mechanism of binarization of swarm intelligence continuous metaheuristics. To evaluate the behavior of our binary operator, the Multi-verse metaheuristic is used and applied to solve the combinatorial problem of the knapsack. The binary algorithm obtained, the binary multi-verse Optimizer (BMVO) shows good performance in solving the most difficult problems of the knapsack.
The integration of machine learning techniques and metaheuristic algorithms is an area of interes... more The integration of machine learning techniques and metaheuristic algorithms is an area of interest due to the great potential for applications. In particular, using these hybrid techniques to solve combinatorial optimization problems (COPs) to improve the quality of the solutions and convergence times is of great interest in operations research. In this article, the db-scan unsupervised learning technique is explored with the goal of using it in the binarization process of continuous swarm intelligence metaheuristic algorithms. The contribution of the db-scan operator to the binarization process is analyzed systematically through the design of random operators. Additionally, the behavior of this algorithm is studied and compared with other binarization methods based on clusters and transfer functions (TFs). To verify the results, the well-known set covering problem is addressed, and a real-world problem is solved. The results show that the integration of the db-scan technique produc...
Fatigue & Fracture of Engineering Materials & Structures, 2017
Open-cell aluminium foams are a relatively new material with interesting uses in different engine... more Open-cell aluminium foams are a relatively new material with interesting uses in different engineering applications. This study investigates the fatigue behaviour and damage accumulation of metal foams via a fatigue analysis (Weibull E-N model), a failure criterion (the relation among the prepeak compressive and tensile slopes, the reduction in the tensile stress, or the reduction in the compressive stress), and a mathematical approach (linear, quadratic, or exponential). As a result of combining the 3 mathematical approaches and 3 failure criteria, different approaches are obtained, analysed, and validated by using experimental data. Finally, the proposed approaches can be used to directly obtain the damage accumulation level for open-cell metal foams under fully reversed cyclic loading as a function of the number of cycles applied, the total strain amplitude, and the initial damage accumulation condition.
Objective: This study was conducted to establish associations among the Candida carriage rate, th... more Objective: This study was conducted to establish associations among the Candida carriage rate, the diversity of Candida species carried and the different caries status of preschool children. Materials and methods: Sixty-one children between 2 and 5 years of age were examined by a single expert examiner and were divided into three groups, the caries-free, moderate caries and severe caries groups, according to the criteria of the International Caries Detection and Assessment System II (ICDAS). Saliva samples were obtained from the members of each group and were plated on Sabouraud agar plates to assess the Candida carriage rates. CHROMagar Candida medium was used for the preliminary screening. Biochemical testing or PCR/sequencing was conducted to identify the different Candida species in the samples. The differences observed were considered significant if the p value was <0.05. Results: The Candida carriage rate and the number of species of this fungus carried were higher in the group with the highest level of caries severity (p < 0.05). Whereas Candida albicans was the most predominant Candida species in the saliva of all of the children, C. dubliniensis was identified only in the most caries-affected group in addition to other rare species of Candida non-albicans. Conclusions: A high salivary Candida carriage rate and the presence of specific species of this fungus (such as C. albicans and C. dubliniensis) appear to be related to the severity of caries experienced by preschool children.
Computer-Aided Civil and Infrastructure Engineering, 2016
Existing computer models used to optimize railway timetables lead to a high complexity when the n... more Existing computer models used to optimize railway timetables lead to a high complexity when the number of analyzed services exceeds a given threshold. A time partitioning technique is proposed which allows line design and timetable optimization and a reduction in the complexity of the problem by considering small time windows of the same or different durations in which the timetables of a small (equal or not) number of running trains are optimized in sequence. Though the optimal solution is not expected to be attained with this method, the analyzed examples demonstrate that the resulting solution is close to the global optimum and practically satisfactory. This technique can be used at the planning and implementation stages. Examples of two real lines are analyzed to show the goodness of the proposed methods. One is the network Madrid-Sevilla-Toledo-Málaga-Valencia-Albacete with a dense traffic of 170 trains per day. The second is the Palencia-Santander
Artemia franciscana es uno de los organismos vivos más utilizados para la alimentación de especie... more Artemia franciscana es uno de los organismos vivos más utilizados para la alimentación de especies en cultivo, debido a que presenta varias proteínas y ácidos grasos insaturados que juegan un rol fundamental en diversas funciones metabólicas de las especies cultivadas. Esta especie corresponde a un crustáceo pequeño branquiópodo, filtrador no selectivo, propio de hábitats acuáticos de elevada salinidad. En la etapa adulta pueden ser especies bisexuales y partenogenéticas, en ambas poblaciones las hembras pueden dar lugar a dos tipos de reproducción, ovovivípara que resulta en un nauplio completamente formado; y ovípara que resulta un cistos que pueden dar una eclosión inmediata o entrar en estado criptobiótico o de diapausa por largos períodos, facilitando la obtención de nauplios durante todo el año. Con el objetivo de establecer las variables de salinidad y temperatura óptimas para la reproducción ovípara y posterior desarrollo de Artemia franciscana, en la zona norte de Chile, se realizó un cultivo experimental con adultos reproductores, los que fueron sometidos a nueve tratamientos con tres réplicas, a diferentes rangos de salinidad (100 g/L, 120 g/L y 140 g/L) y temperatura (20 °C, 25 °C y 30 °C), donde los cistos obtenidos se colectaron diariamente y se almacenaron durante dos semanas para después determinar la calidad de estos sobre la base del porcentaje y eficiencia de eclosión, aplicándose a los datos obtenidos un análisis de varianza de dos vías (ANOVA) para establecer diferencias significativas entre los tratamientos. Los resultados del análisis establecieron que existe diferencia significativa entre la salinidad y temperatura de experimentación, debido a que por separado solamente la salinidad presenta una incidencia en la reproducción. Se pone de manifiesto que los parámetros fisicoquímicos adecuados para reproducción ovípara de A. franciscana es de 120 g/L a 25 °C, debido a que presenta una diferencia significativa al nivel p < 0,054.
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