| Records |
| Author |
Melo, I.C.; Alves, P.N.; Queiroz, G.A.; Yushimito, W.; Pereira, J. |
| Title |
Do We Consider Sustainability When We Measure Small and Medium Enterprises' (SMEs') Performance Passing through Digital Transformation? |
Type |
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Year  |
2023 |
Publication |
Sustainability |
Abbreviated Journal |
Sustainability |
| Volume |
15 |
Issue |
6 |
Pages |
4917 |
| Keywords |
digitalization; small- and medium-sized enterprises (SMEs); Industry 4; 0; topic modeling; latent dirichlet allocation (LDA); triple bottom line of sustainability |
| Abstract |
Small-medium enterprises (SMEs) represent 90% of business globally. Digital Transformation (DT) affects SMEs differently from larger companies because although SMEs have more flexibility and agility for adapting to new circumstances, they also have more limited resources and specialization capabilities. Thus, it is fundamental to measure SMEs' performance considering different perspectives. Here, we describe and analyze the state-of-the-art of DT in SMEs, focusing on performance measurement. We center on whether the tools used by SMEs encompass the triple bottom line of sustainability (i.e., environmental, social, and economic aspects). To do so, in December 2021, we performed a comprehensive systematic literature review (SLR) on the Web of Science and Scopus. In addition, we also explored a novel approach for SLR: topic modeling with a machine learning technique (Latent Dirichlet Allocation). The differences and interchangeability of both methods are discussed. The findings show that sustainability is treated as a separate topic in the literature. The social and environmental aspects are the most neglected. This paper contributes to sustainable development goals (SDGs) 1, 5, 8, 9, 10, and 12. A conceptual framework and future research directions are proposed. Thus, this paper is also valuable for policymakers and SMEs switching their production paradigm toward sustainability and DT. |
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| ISSN |
2071-1050 |
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| Notes |
WOS:000958416000001 |
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| Call Number |
UAI @ alexi.delcanto @ |
Serial |
1770 |
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| Author |
Melo, I.C.; Queiroz, G.A.; Junior, P.N.A.; de Sousa, T.B.; Yushimito, W.F.; Pereira, J. |
| Title |
Sustainable digital transformation in small and medium enterprises (SMEs): A review on performance |
Type |
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| Year |
2023 |
Publication |
Heliyon |
Abbreviated Journal |
Heliyon |
| Volume |
9 |
Issue |
3 |
Pages |
e13908 |
| Keywords |
Digitalization; Small and medium-sized enterprises (SMEs); Industry 40Triple bottom line (TBL) of sustainability; Sustainable development goals (SDG) |
| Abstract |
Small and medium enterprises (SMEs) are responsible for 90% of all business and 50% of employment globally, mostly female jobs. Therefore, measuring SMEs' performance under the digital transformation (DT) through methods that encompass sustainability represents an essential tool for reducing poverty and gender inequality (United Nations Sustainable Development Goals). We aimed to describe and analyze the state-of-art performance evaluations of digital transformation in SMEs, mainly focusing on performance measurement. Also, we aimed to determine whether the tools encompass the three pillars of sustainability (environmental, social, and economic). Through a systematic literature review (SLR), a search on Web of Science (WoS) and Scopus resulted in the acceptance of 74 peer-reviewed papers published until December 2021. Additionally, a bibliometrics investigation was executed. Although there was no time restriction, the oldest paper was published in 2016, indicating that DT is a new research topic with increasing interest. Italy, China, and Finland are the countries that have the most published on the theme. Based on the results, a conceptual framework is proposed. Also, two future research directions are presented and discussed, one for theoretical and another for practical research. Among the theoretical development, it is essential to work on a widely accepted SME definition. Among the practical research, nine directions are identified-e.g., applying big data, sectorial and regional prioritization, cross-temporal investigations etc. Researchers can follow the presented avenues and roads to guide their researchers toward the most relevant topics with the most urgent necessity of investigation. |
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| ISSN |
2405-8440 |
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| Notes |
WOS:000968115200001 |
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UAI @ alexi.delcanto @ |
Serial |
1782 |
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| Author |
Pereira, J.; Ritt, M. |
| Title |
Exact and heuristic methods for a workload allocation problem with chain precedence constraints |
Type |
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| Year |
2023 |
Publication |
European Journal Of Operational Research |
Abbreviated Journal |
Eur. J. Oper. Res. |
| Volume |
309 |
Issue |
1 |
Pages |
387-398 |
| Keywords |
Manufacturing; Assembly line balancing; Worker allocation; Dynamic programming; Branch and bound |
| Abstract |
Industrial manufacturing is often organized in assembly lines where a product is assembled on a se-quence of stations, each of which executes some of the assembly tasks. A line is balanced if the maximum total execution time of any station is minimal. Commonly, the task execution order is constrained by precedences, and task execution times are independent of the station performing the task. Here, we con -sider a recent variation, called the “(Calzedonia) Workload Allocation Problem” (WAP), where the prece-dences form a chain, and the execution time of a task depends on the worker executing it. This problem was recently proposed by Battarra et al. (2020) and it is a special case of the Assembly Line Worker As-signment and Balancing Problem Miralles et al. (2007) where precedence relations are arbitrary. In this paper we consider the computational complexity of the problem and prove its NP-hardness. To solve the problem, we provide different lower bounds and exact and heuristic procedures. The performance of the proposed methods is tested on previously proposed instances and on new, larger instances with the same characteristics. The results show that the proposed methods can solve instances with up to about 40 0 0 tasks and 29 workers, doubling the size of the instances that previously could be solved to optimality. |
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Edition |
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| ISSN |
0377-2217 |
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Conference |
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| Notes |
WOS:000970067900001 |
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| Call Number |
UAI @ alexi.delcanto @ |
Serial |
1794 |
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| Author |
Pereira, J.; Ritt, M |
| Title |
A note on “Algorithms for the Calzedonia workload allocation problem” |
Type |
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| Year |
2022 |
Publication |
Journal of the Operational Research Society |
Abbreviated Journal |
J. Oper. Res. Soc. |
| Volume |
73 |
Issue |
6 |
Pages |
1420-1422 |
| Keywords |
Assembly line balancing; worker allocation; dynamic programming |
| Abstract |
Battarra et al. recently proposed a novel assembly line balancing problem with applications to the apparel industry, where the tasks are performed in a fixed order. To solve the problem, one has to assign workers and tasks to the workstations with the objective of maximising the throughput of the assembly line. In this paper, we provide dynamic programming formulations for the general problem and some special cases. We then use these formulations to develop an exact solution approach that optimally solves the instances in Battarra et al. within seconds. |
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Edition |
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| ISSN |
0160-5682 |
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Conference |
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| Notes |
WOS:000627308200001 |
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| Call Number |
UAI @ alexi.delcanto @ |
Serial |
1351 |
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| Author |
Alvarez-Miranda, E.; Pereira, J. |
| Title |
A Districting Application with a Quality of Service Objective |
Type |
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| Year |
2022 |
Publication |
Mathematics |
Abbreviated Journal |
Mathematics |
| Volume |
10 |
Issue |
1 |
Pages |
13 |
| Keywords |
districtin; glast-mile delivery; hybrid heuristics |
| Abstract |
E-commerce sales have led to a considerable increase in the demand for last-mile delivery companies, revealing several problems in their logistics processes. Among these problems, are not meeting delivery deadlines. For example, in Chile, the national consumer service (SERNAC) indicated that in 2018, late deliveries represented 23% of complaints in retail online sales and were the second most common reason for complaints. Some of the causes are incorrectly designed delivery zones because in many cases, these delivery zones do not account for the demographic growth of cities. The result is an imbalanced workload between different zones, which leads to some resources being idle while others fail to meet their workload in satisfactory conditions. The present work proposes a hybrid method for designing delivery zones with an objective based on improving the quality of express delivery services. The proposed method combines a preprocess based on the grouping of demand in areas according to the structure of the territory, a heuristic that generates multiple candidates for the distribution zones, and a mathematical model that combines the different distribution zones generated to obtain a final territorial design. To verify the applicability of the proposed method, a case study is considered based on the real situation of a Chilean courier company with low service fulfillment in its express deliveries. The results obtained from the computational experiments show the applicability of the method, highlighting the validity of the aggregation procedure and improvements in the results obtained using the hybrid method compared to the initial heuristic. The final solution improves the ability to meet the conditions associated with express deliveries, compared with the current situation, by 12 percentage points. The results also allow an indicative sample of the critical service factors of a company to be obtained, identifying the effects of possible changes in demand or service conditions. |
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2227-7390 |
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| Notes |
WOS:000751158600001 |
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| Call Number |
UAI @ alexi.delcanto @ |
Serial |
1529 |
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| Author |
Yuraszeck, F.; Mejia, G.; Pereira, J.; Vila, M. |
| Title |
A Novel Constraint Programming Decomposition Approach for the Total Flow Time Fixed Group Shop Scheduling Problem |
Type |
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| Year |
2022 |
Publication |
Mathematics |
Abbreviated Journal |
Mathematics |
| Volume |
10 |
Issue |
3 |
Pages |
329 |
| Keywords |
scheduling; fixed group shop; group shop; constraint programming |
| Abstract |
This work addresses a particular case of the group shop scheduling problem (GSSP) which will be denoted as the fixed group shop scheduling problem (FGSSP). In a FGSSP, job operations are divided into stages and each stage has a set of machines associated to it which are not shared with the other stages. All jobs go through all the stages in a specific order, where the operations of the job at each stage need to be finished before the job advances to the following stage, but operations within a stage can be performed in any order. This setting is common in companies such as leaf spring manufacturers and other automotive companies. To solve the problem, we propose a novel heuristic procedure that combines a decomposition approach with a constraint programming (CP) solver and a restart mechanism both to avoid local optima and to diversify the search. The performance of our approach was tested on instances derived from other scheduling problems that the FGSSP subsumes, considering both the cases with and without anticipatory sequence-dependent setup times. The results of the proposed algorithm are compared with off-the-shelf CP and mixed integer linear programming (MILP) methods as well as with the lower bounds derived from the study of the problem. The experiments show that the proposed heuristic algorithm outperforms the other methods, specially on large-size instances with improvements of over 10% on average. |
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2227-7390 |
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Conference |
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| Notes |
WOS:000756126100001 |
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| Call Number |
UAI @ alexi.delcanto @ |
Serial |
1549 |
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| Author |
Alvarez-Miranda, E.; Pereira, J.; Vargas, C.; Vila, M. |
| Title |
Variable-depth local search heuristic for assembly line balancing problems |
Type |
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| Year |
2022 |
Publication |
International Journal Of Production Research |
Abbreviated Journal |
Int. J. Prod. Res. |
| Volume |
61 |
Issue |
9 |
Pages |
3103-3121 |
| Keywords |
Assembly lines; Manufacturing; simple assembly line balancing; local search; variable-depth local search |
| Abstract |
Assembly lines are production flow systems wherein activities are organised around a line consisting of various workstations through which the product flows. At each station, the product is assembled through a subset of operations. The assembly line balancing problem (ALBP) consists of allocating operations between stations to maximise the system efficiency. In this study, a variable-depth local search algorithm is proposed for solving simple assembly line balancing problems (SALBPs), which are the most widely studied versions of the ALBP. Although the state-of-the-art techniques for solving the SALBP consist of exact enumeration-based methods or heuristics, this paper proposes a local search-based heuristic using variable-length sequences that allow the solution space to be efficiently explored. The proposed algorithm improves the best solution known for multiple instances reported in the literature, indicating that its efficiency is comparable to those of the state-of-the-art method for solving the SALBP. Moreover, the characteristics of the instances for which the proposed procedure provides a better solution than previously reported construction procedures are investigated. |
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Edition |
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| ISSN |
0020-7543 |
ISBN |
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| Notes |
WOS:000800928700001 |
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| Call Number |
UAI @ alexi.delcanto @ |
Serial |
1578 |
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| Author |
Sandoval, G.; Alvarez-Miranda, E.; Pereira, J.; Rios-Mercado, R.Z.; Diaz, J.A. |
| Title |
A novel districting design approach for on-time last-mile delivery: An application on an express postal company |
Type |
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| Year |
2022 |
Publication |
Omega-International Journal Of Management Science |
Abbreviated Journal |
Omega-Int. J. Manage. Sci. |
| Volume |
113 |
Issue |
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Pages |
102687 |
| Keywords |
Districting; Last-mile delivery; Postal delivery; Supply chain management; Heuristics |
| Abstract |
Last-mile logistics corresponds to the last leg of the supply chain, i.e., the delivery of goods to final cus-tomers, and they comprise the core activities of postal and courier companies. Because of their role in the supply chain, last-mile operations are critical for the perception of customers regarding the perfor-mance of the whole logistic process. In this sense, the sustained growth of e-commerce, which has been abruptly catalyzed by the irruption of the COVID-19 pandemic, has hanged the habits of customers and overtaxed the operational side of delivery companies, hindering their viability and forcing their adap-tation to the novel conditions. Many of these habits will remain after we overcome the sanitary crisis, which will permanently reshape the structure and emphasis of postal supply chains, demanding compa-nies to implement organizational and operational changes to adapt to these new challenges. In this work we address a last-mile logistic design problem faced by a courier and delivery company in Chile, although the same problem is likely to arise in the last-mile delivery operation of other postal companies, in particular in the operation of express delivery services. The operational structure of the company is based on the division of an urban area into smaller territories (districts) and the outsourcing of the delivery operation of each territory to a last-mile contractor. Because of the increasing volume of postal traffic and a decreasing performance of the service, in particular for the case of express deliveries, the company is forced to redesign its current territorial arrangement. Such redesign results in a novel optimization problem that resembles a classical districting problem with the additional quality of service requirements. This novel problem is first formulated as a mathematical programming model and then a specially tailored heuristic is designed for solving it. The proposed approach is tested on instances from the real-life case study, and the obtained results show significant improvements in terms of the percent-age of on-time deliveries achieved by the proposed solution when compared to the current districting design of the company. By performing a sensitivity analysis considering different levels of demand, we show that the proposed approach is effective in providing districting designs capable of enduring signifi-cant increases in the demand for express postal services. |
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0305-0483 |
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| Notes |
WOS:000809666900001 |
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UAI @ alexi.delcanto @ |
Serial |
1605 |
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| Author |
Alvarez-Miranda, E.; Chace, S.; Pereira, J. |
| Title |
Assembly line balancing with parallel workstations |
Type |
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| Year |
2021 |
Publication |
International Journal Of Production Research |
Abbreviated Journal |
Int. J. Prod. Res. |
| Volume |
59 |
Issue |
21 |
Pages |
6486-6506 |
| Keywords |
Line balancing; parallel stations; dynamic programming; hybrid metaheuristic; matheuristic |
| Abstract |
The simple assembly line balancing problem (SALBP) considers work division among different workstations of a serially arranged assembly process to maximise its efficiency under workload (cumulative) and technological (precedence) constraints. In this work, we consider a variant of the SALBP which allows parallel workstations. To study the effect of parallel stations, we propose a new problem (the parallel station assembly line balancing problem or PSALBP) in which the objective is to minimise the number of parallel stations required to obtain the maximum theoretical efficiency of the assembly process. We study the complexity of the problem and identify a polynomially solvable case. This result is then used as a building block for the development of a heuristic solution procedure. Finally, we carry out a computational experiment to identify the characteristics of assembly lines that may benefit from station paralleling and to evaluate the performance of the proposed heuristic. |
| Address |
[alvarez-Miranda, Eduardo] Univ Talca, Fac Engn, Dept Ind Engn, Curico, Chile, Email: jorge.pereira@uai.cl |
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Taylor & Francis Ltd |
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English |
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0020-7543 |
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WOS:000569837900001 |
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UAI @ alexi.delcanto @ |
Serial |
1243 |
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| Author |
Cohen, Y.M.; Keskinocak, P.; Pereira, J. |
| Title |
A note on the flowtime network restoration problem |
Type |
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| Year |
2021 |
Publication |
IISE Transactions |
Abbreviated Journal |
IISE Trans. |
| Volume |
53 |
Issue |
12 |
Pages |
1351-1352 |
| Keywords |
Scheduling; network construction planning; emergency restoration operations; deliveryman problem; traveling repairman problem |
| Abstract |
The flowtime network restoration problem was introduced by Averbakh and Pereira (2012) who presented a Minimum Spanning Tree heuristic, two local search procedures, and an exact branch-and-bound algorithm. This note corrects the computational results in Averbakh and Pereira (2012). |
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2472-5854 |
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WOS:000617722200001 |
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UAI @ alexi.delcanto @ |
Serial |
1343 |
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Campos-Valdes, C.; Alvarez-Miranda, E.; Quiroga, MM; Pereira, J.; Duran, FL. |
| Title |
The Impact of Candidates' Profile and Campaign Decisions in Electoral Results: A Data Analytics Approach |
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| Year |
2021 |
Publication |
Mathematics |
Abbreviated Journal |
Mathematics |
| Volume |
9 |
Issue |
8 |
Pages |
902 |
| Keywords |
Chilean parliamentary election; candidate profiles; campaign efforts; territorial deployment |
| Abstract |
In recent years, a wide range of techniques has been developed to predict electoral results and to measure the influence of different factors in these results. In this paper, we analyze the influence of the political profile of candidates (characterized by personal and political features) and their campaign effort (characterized by electoral expenditure and by territorial deployment strategies retrieved from social networks activity) on the electoral results. This analysis is carried out by using three of the most frequent data analyitcs algorithms in the literature. For our analysis, we consider the 2017 Parliamentary elections in Chile, which are the first elections after a major reform of the electoral system, that encompassed a transition from a binomial to a proportional system, a modification of the districts' structure, an increase in the number of seats, and the requirement of gender parity in the lists of the different coalitions. The obtained results reveal that, regardless of the political coalition, the electoral experience of candidates, in particular in the same seat they are running for (even when the corresponding district is modified), is by large the most influential factor to explain the electoral results. However, the attained results show that the influence of other features, such as campaign expenditures, depends on the political coalition. Additionally, by means of a simulation procedure, we show how different levels of territorial deployment efforts might impact on the results of candidates. This procedure could be used by parties and coalitions when planning their campaign strategies. |
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2227-7390 |
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WOS:000644524000001 |
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UAI @ alexi.delcanto @ |
Serial |
1377 |
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| Author |
Opazo, D.; Moreno, S.; Alvarez-Miranda, E.; Pereira, J. |
| Title |
Analysis of First-Year University Student Dropout through Machine Learning Models: A Comparison between Universities |
Type |
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| Year |
2021 |
Publication |
Mathematics |
Abbreviated Journal |
Mathematics |
| Volume |
20 |
Issue |
9 |
Pages |
2599 |
| Keywords |
machine learning; first-year student dropout; universities |
| Abstract |
Student dropout, defined as the abandonment of a high education program before obtaining the degree without reincorporation, is a problem that affects every higher education institution in the world. This study uses machine learning models over two Chilean universities to predict first-year engineering student dropout over enrolled students, and to analyze the variables that affect the probability of dropout. The results show that instead of combining the datasets into a single dataset, it is better to apply a model per university. Moreover, among the eight machine learning models tested over the datasets, gradient-boosting decision trees reports the best model. Further analyses of the interpretative models show that a higher score in almost any entrance university test decreases the probability of dropout, the most important variable being the mathematical test. One exception is the language test, where a higher score increases the probability of dropout. |
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2227-7390 |
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UAI @ alexi.delcanto @ |
Serial |
1463 |
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| Author |
Alvarez-Miranda, E.; Pereira, J.; Torrez-Meruvia H.; Vila, M. |
| Title |
A Hybrid Genetic Algorithm for the Simple Assembly Line Balancing Problem with a Fixed Number of Workstations |
Type |
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| Year |
2021 |
Publication |
Mathematics |
Abbreviated Journal |
Mathematics |
| Volume |
9 |
Issue |
17 |
Pages |
2157 |
| Keywords |
assembly lines; manufacturing; line balancing; hybrid genetic algorithm |
| Abstract |
The assembly line balancing problem is a classical optimisation problem whose objective is to assign each production task to one of the stations on the assembly line so that the total efficiency of the line is maximized. This study proposes a novel hybrid method to solve the simple version of the problem in which the number of stations is fixed, a problem known as SALBP-2. The hybrid differs from previous approaches by encoding individuals of a genetic algorithm as instances of a modified problem that contains only a subset of the solutions to the original formulation. These individuals are decoded to feasible solutions of the original problem during fitness evaluation in which the resolution of the modified problem is conducted using a dynamic programming based approach that uses new bounds to reduce its state space. Computational experiments show the efficiency of the method as it is able to obtain several new best-known solutions for some of the benchmark instances used in the literature for comparison purposes. |
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| ISSN |
2227-7390 |
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| Notes |
WOS:000694360700001 |
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| Call Number |
UAI @ alexi.delcanto @ |
Serial |
1466 |
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| Author |
Moreno, S.; Pereira, J.; Yushimito, W. |
| Title |
A hybrid K-means and integer programming method for commercial territory design: a case study in meat distribution |
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| Year |
2020 |
Publication |
Annals Of Operations Research |
Abbreviated Journal |
Ann. Oper. Res. |
| Volume |
286 |
Issue |
1-2 |
Pages |
87-117 |
| Keywords |
Territorial design; Clustering; K-means; Integer programming; Case study |
| Abstract |
The objective of territorial design for a distribution company is the definition of geographic areas that group customers. These geographic areas, usually called districts or territories, should comply with operational rules while maximizing potential sales and minimizing incurred costs. Consequently, territorial design can be seen as a clustering problem in which clients are geographically grouped according to certain criteria which usually vary according to specific objectives and requirements (e.g. costs, delivery times, workload, number of clients, etc.). In this work, we provide a novel hybrid approach for territorial design by means of combining a K-means-based approach for clustering construction with an optimization framework. The K-means approach incorporates the novelty of using tour length approximation techniques to satisfy the conditions of a pork and poultry distributor based in the region of Valparaiso in Chile. The resulting method proves to be robust in the experiments performed, and the Valparaiso case study shows significant savings when compared to the original solution used by the company. |
| Address |
[Moreno, Sebastian; Pereira, Jordi; Yushimito, Wilfredo] Univ Adolfo Ibanez, Fac Engn & Sci, Av Padre Hurtado 750, Vina Del Mar, Chile, Email: sebastian.moreno@uai.cl; |
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Springer |
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English |
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| ISSN |
0254-5330 |
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| Notes |
WOS:000511564300005 |
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| Call Number |
UAI @ eduardo.moreno @ |
Serial |
1105 |
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| Author |
Mejia, G.; Pereira, J. |
| Title |
Multiobjective scheduling algorithm for flexible manufacturing systems with Petri nets |
Type |
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| Year |
2020 |
Publication |
Journal Of Manufacturing Systems |
Abbreviated Journal |
J. Manuf. Syst. |
| Volume |
54 |
Issue |
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Pages |
272-284 |
| Keywords |
Machine scheduling; Multi-objective optimization; Petri nets |
| Abstract |
In this work, we focus on general multi-objective scheduling problems that can be modeled using a Petri net framework. Due to their generality, Petri nets are a useful abstraction that captures multiple characteristics of real-life processes. To provide a general solution procedure for the abstraction, we propose three alternative approaches using an indirect scheme to represent the solution: (1) a genetic algorithm that combines two objectives through a weighted fitness function, (2) a non dominated sorting genetic algorithm (NSGA-II) that explicitly addresses the multi-objective nature of the problem and (3) a multi-objective local search approach that simultaneously explores multiple candidate solutions. These algorithms are tested in an extensive computational experiment showing the applicability of this general framework to obtain quality solutions. |
| Address |
[Mejia, Gonzalo] Univ La Sabana, Fac Engn, Campus Puente del Comun, Chia, Colombia, Email: gonzalo.mejia@unisabana.edu.co; |
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Elsevier Sci Ltd |
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English |
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| ISSN |
0278-6125 |
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| Notes |
WOS:000521511500021 |
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| Call Number |
UAI @ eduardo.moreno @ |
Serial |
1154 |
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| Author |
Ritt, M.; Pereira, J. |
| Title |
Heuristic and exact algorithms for minimum-weight non-spanning arborescences |
Type |
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| Year |
2020 |
Publication |
European Journal Of Operational Research |
Abbreviated Journal |
Eur. J. Oper. Res. |
| Volume |
287 |
Issue |
1 |
Pages |
61-75 |
| Keywords |
Minimum-weight non-spanning arborescence; Heuristic; Iterated Local Search; Branch-and-cut |
| Abstract |
We address the problem of finding an arborescence of minimum total edge weight rooted at a given vertex in a directed, edge-weighted graph. If the arborescence must span all vertices the problem is solvable in polynomial time, but the non-spanning version is NP-hard. We propose reduction rules which determine vertices that are required or can be excluded from optimal solutions, a modification of Edmonds algorithm to construct arborescences that span a given set of selected vertices, and embed this procedure into an iterated local search for good vertex selections. Moreover, we propose a cutset-based integer linear programming formulation, provide different linear relaxations to reduce the number of variables in the model and solve the reduced model using a branch-and-cut approach. We give extensive computational results showing that both the heuristic and the exact methods are effective and obtain better solutions on instances from the literature than existing approaches, often in much less time. (C) 2020 Elsevier B.V. All rights reserved. |
| Address |
[Ritt, Marcus] Univ Fed Rio Grande do Sul, Inst Informat, Av Bento Goncalves 9500, Porto Alegre, RS, Brazil, Email: marcus.ritt@inf.ufrgs.br; |
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Elsevier |
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English |
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| ISSN |
0377-2217 |
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| Notes |
WOS:000541072800005 |
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UAI @ eduardo.moreno @ |
Serial |
1187 |
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| Author |
Alvarez-Miranda, E.; Campos-Valdes, C.; Quiroga, M.M.; Moreno-Faguett, M.; Pereira, J. |
| Title |
A Multi-Criteria Pen for Drawing Fair Districts: When Democratic and Demographic Fairness Matter |
Type |
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| Year |
2020 |
Publication |
Mathematics |
Abbreviated Journal |
Mathematics |
| Volume |
8 |
Issue |
9 |
Pages |
27 pp |
| Keywords |
multi-criteria optimization; OR applications; malapportionment; districting; electoral system |
| Abstract |
Electoral systems are modified by individuals who have incentives to bias the rules for their political advantage (i.e., gerrymandering). To prevent gerrymandering, legislative institutions can rely on mathematical tools to guarantee democratic fairness and territorial contiguity. These tools have been successfully used in the past; however, there is a need to accommodate additional meanings of the term fairness within the electoral systems of modern democracies. In this paper, we present an optimization framework that considers multiple criteria for drawing districts and assigning the number of representatives. Besides some typical districting criteria (malapportionment and contiguity), we introduce novel criteria for ensuring territorial equilibrium and incentives for candidates to deploy their representation efforts fairly during their campaign and period in office. We test the method, which we denote as Multi-criteria Pen, in a recent and a forthcoming reform of the Chilean electoral system. The results show the potential of our tool to improve the current territorial design and offers insights on the motivations, objectives, and deficiencies of both reform plans. |
| Address |
[Alvarez-Miranda, Eduardo; Moreno-Faguett, Magas] Univ Talca, Fac Engn, Dept Ind Engn, Campus Curico, Curico 3341717, Chile, Email: ealvarez@utalca.cl; |
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Mdpi |
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English |
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2227-7390 |
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| Notes |
WOS:000580771600001 |
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UAI @ alexi.delcanto @ |
Serial |
1246 |
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Osorio-Valenzuela, L.; Pereira, J.; Quezada, F.; Vasquez, O.C. |
| Title |
Minimizing the number of machines with limited workload capacity for scheduling jobs with interval constraints |
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2019 |
Publication |
Applied Mathematical Modelling |
Abbreviated Journal |
Appl. Math. Model. |
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74 |
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512-527 |
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Scheduling; Parallel machines; Interval and workload constraints; Branch-and-price |
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In this paper, we consider a parallel machine scheduling problem in which machines have a limited workload capacity and jobs have deadlines and release dates. The problem is motivated by the operation of energy storage management systems for microgrids under emergency conditions and generalizes some problems that have already been studied in the literature for their theoretical value. In this work, we propose heuristic and exact algorithms to solve the problem. The heuristics are adaptations of classical bin packing heuristics in which additional conditions on the feasibility of a solution are imposed, whereas the exact method is a branch-and-price approach. The results show that the branch-andprice approach is able to optimally solve random instances with up to 250 jobs within a time limit of one hour, while the heuristic procedures provide near optimal solution within reduced running times. Finally, we also provide additional complexity results for a special case of the problem. (C) 2019 Elsevier Inc. All rights reserved. |
| Address |
[Osorio-Valenzuela, Luis] Univ Santiago Chile, Elect Engn Dept, Santiago, Chile, Email: luis.osoriov@usach.cl; |
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Elsevier Science Inc |
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English |
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0307-904x |
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| Notes |
WOS:000474317800031 |
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| Call Number |
UAI @ eduardo.moreno @ |
Serial |
1013 |
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| Author |
Alvarez-Miranda, E.; Pereira, J. |
| Title |
On the complexity of assembly line balancing problems |
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| Year |
2019 |
Publication |
Computers & Operations Research |
Abbreviated Journal |
Comput. Oper. Res. |
| Volume |
108 |
Issue |
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Pages |
182-186 |
| Keywords |
Line balancing; Complexity; Bin packing |
| Abstract |
Assembly line balancing is a family of combinatorial optimization problems that has been widely studied in the literature due to its simplicity and industrial applicability. Most line balancing problems are NP-hard as they subsume the bin packing problem as a special case. Nevertheless, it is common in the line balancing literature to cite [A. Gutjahr and G. Nemhauser, An algorithm for the line balancing problem, Management Science 11 (1964) 308-315] in order to assess the computational complexity of the problem. Such an assessment is not correct since the work of Gutjahr and Nemhauser predates the concept of NP-hardness. This work points at over 50 publications since 1995 with the aforesaid error. (C) 2019 Elsevier Ltd. All rights reserved. |
| Address |
[Alvarez-Miranda, Eduardo] Univ Talca, Dept Ind Engn, Curico, Chile, Email: jorge.pereira@uai.cl |
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Pergamon-Elsevier Science Ltd |
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English |
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| ISSN |
0305-0548 |
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| Notes |
WOS:000471733300014 |
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| Call Number |
UAI @ eduardo.moreno @ |
Serial |
1015 |
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| Author |
Pereira, J. |
| Title |
The robust (minmax regret) assembly line worker assignment and balancing problem |
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| Year |
2018 |
Publication |
Computers & Operations Research |
Abbreviated Journal |
Comput. Oper. Res. |
| Volume |
93 |
Issue |
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Pages |
27-40 |
| Keywords |
Production; Line balancing; Robust optimization; Minmax regret |
| Abstract |
Line balancing aims to assign the assembly tasks to the stations that compose the assembly line. A recent body of literature has been devoted to heterogeneity in the assembly process introduced by different workers. In such an environment, task times depend on the worker performing the operation and the problem aims at assigning tasks and workers to stations in order to maximize the throughput of the line. In this work, we consider an interval data version of the assembly line worker assignment and balancing problem (ALWABP) in which it is assumed that lower and upper bounds for the task times are known, and the objective is to find an assignment of tasks and workers to the workstations such that the absolute maximum regret among all of the possible scenarios is minimized. The relationship with other interval data minmax regret (IDMR) problems is investigated, the inapplicability of previous approximation methods is studied, regret evaluation is considered, and exact and heuristic solution methods are proposed and analyzed. The results of the proposed methods are compared in a computational experiment, showing the applicability of the method and the theoretical results to solve the problem under study. Additionally, these results are not only applicable to the problem in hand, but also to a more general class of problems. (C) 2018 Elsevier Ltd. All rights reserved. |
| Address |
[Pereira, Jordi] Univ Adolfo Ibanez, Dept Sci & Engn, Av Padre Hurtado 750,Off C216, Vina Del Mar, Chile, Email: jorge.pereira@uai.cl |
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Pergamon-Elsevier Science Ltd |
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English |
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0305-0548 |
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| Notes |
WOS:000427339800003 |
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| Call Number |
UAI @ eduardo.moreno @ |
Serial |
838 |
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