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- Waste collection routing-limited multiple landfills and heterogeneous fleetPublication . Rodrigues, Ana Maria; Soeiro Ferreira, JoséThis article deals with a real-life waste collection routing problem. To efficiently plan waste collection, large municipalities may be partitioned into convenient sectors and only then can routing problems be solved in each sector. Three diverse situations are described, resulting in three different new models. In the first situation, there is a single point of waste disposal from where the vehicles depart and to where they return. The vehicle fleet comprises three types of collection vehicles. In the second, the garage does not match any of the points of disposal. The vehicle is unique and the points of disposal (landfills or transfer stations) may have limitations in terms of the number of visits per day. In the third situation, disposal points are multiple (they do not coincide with the garage), they are limited in the number of visits, and the fleet is composed of two types of vehicles. Computational results based not only on instances adapted from the literature but also on real cases are presented and analyzed. In particular, the results also show the effectiveness of combining sectorization and routing to solve waste collection problems.
- A resectorization of fire brigades in the north of PortugalPublication . Lima, Maria Margarida; Ozturk, E. Goksu; Sousa, FIlipe; Lopes, Isabel Cristina; Teles Oliveira, Cristina; Rodrigues, Ana Maria; Catarina Nunes, Ana; Soeiro Ferreira, JoséSectorization can be regarded as a division of a territory into smaller regions to deal with a complex problem involving multiple-criteria. Resectorization intends to achieve another sectorization, according to some new conditions but avoiding substantial changes. An example of this can be the distribution of geographical areas by fire brigades. In Portugal, fire brigades must protect and rescue the population in the areas surrounding their fire stations. So we will use the current sectorization, the geographic and population characteristics of the areas and the fire brigades’ response capacity to provide an optimised resectorization, in order to decrease rescue time. To achieve that, we will use a decision support system using different optimisation methods, such as Non-dominated Sorting Genetic Algorithm (NSGA II), which provides an effective sectorization concerning compactness and equilibrium criteria.
- Sectorization for managing maintenance techniciansPublication . Lopes, Isabel Cristina; Rodrigues, Ana Maria; Oliveira, Cristina; Soeiro Ferreira, José; Cortinhal, Maria Joãobetter organization of the region, or to simplify a large problem into smaller sub-problems, or to obtain groups with similar characteristics. To evaluate the quality of the solutions, three criteria are commonly used: Equilibrium (the sectors should be identical portions of the whole), Compactness (regular forms like circles are preferred, avoiding sectors shaped with ‘tentacles’), and Contiguity (avoid sectors divided into portions). Depending on the application, other criteria can also be considered, therefore multicriteria approaches should be used. Sectorization problems can arise when designing political districts, defining sales territories, managing routes for distribution of goods or collecting municipal waste, assigning neighborhoods to schools, locating health care services, police stations, or fire brigades. This talk will address the sectorization in an elevator maintenance company, where the definition of the zones assigned to each technician have an impact on the company’s efficiency and quality of service. In order to define the best sectorization, not only the maintenance plan should be considered, but also the unplanned interventions. We will discuss the different solution methods that can be applied to this case.
- Creating homogeneous sectors: criteria and applications of sectorizationPublication . Lopes, Isabel Cristina; Lima, Maria Margarida; Ozturk, E. Goksu; Rodrigues, Ana Maria; Nunes, Ana Catarina; Oliveira, Cristina; Soeiro Ferreira, José; Rocha, PedroSectorization is the process of grouping a set of previously defined basic units (points or small areas) into a fixed number of sectors. Sectorization is also known in the literature as districting or territory design, and is usually performed to optimize one or more criteria regarding the geographic characteristics of the territory and the planning purposes of sectors. The most common criteria are equilibrium, compactness and contiguity, which can be measured in many ways. Sectorization is similar to clustering but with a different motivation. Both aggregate smaller units into groups. But, while clustering strives for inner similarity of data, sectorization aims at outer homogeneity [1]. In clustering, groups should be very different from each other, and similar points are classified in the same cluster. In sectorization, groups should be very similar to each other, and therefore very different points can be grouped in the same sector. We classify sectorization problems into four types: basic sectorization, sectorization with service centers, resectorization, and dynamic sectorization. A Decision Support System for Sectorization, D3S, is being developed to deal with these four types of problems. Multi-objective genetic algorithms were implemented in D3S using Python, and a user-friendly web interface was developed using Django. Several applications can be solved with D3S, such as political districting, sales territory design, delivery service zones, and assignment of fire stations and health services to the population.
- Sectors and routes in solid waste collectionPublication . Rodrigues, Ana Maria; Soeiro Ferreira, JoséCollecting and transporting solid waste is a constant problem for municipalities and populations in general. Waste management should take into account the preservation of the environment and the reduction of costs. The goal with this paper is to address a real-life solid waste problem. The case reveals some general and specific characteristics which are not rare, but are not widely addressed in the literature. Furthermore, new methods and models to deal with sectorization and routing are introduced, which can be extended to other applications. Sectorization and routing are tackled following a two-phase approach. In the first phase, a new method is described for sectorization based on electromagnetism and Coulomb’s Law. The second phase addresses the routing problems in each sector. The paper addresses not only territorial division, but also the frequency with which waste is collected, which is a critical issue in these types of applications. Special characteristics related to the number and type of deposition points were also a motivation for this work. A new model for a Mixed Capacitated Arc Routing Problem with Limited Multi-Landfills is proposed and tested in real instances. The computational results achieved confirm the effectiveness of the entire approach.
- Measures in Sectorization ProblemsPublication . Rodrigues, Ana Maria; Soeiro Ferreira, JoséSectorization means dividing a whole into parts (sectors), a procedure that occurs in many contexts and applications, usually to achieve some goal or to facilitate an activity. The objective may be a better organization or simplification of a large problem into smaller sub-problems. Examples of applications are political districting and sales territory division. When designing/comparing sectors some characteristics such as contiguity, equilibrium and compactness are usually considered. This paper presents and describes new generic measures and proposes a new measure, desirability, connected with the idea of preference.
- Sectorization: measures and an electromagnetism based approachPublication . Rodrigues, Ana Maria; Soeiro Ferreira, JoséSectorization means dividing a set of basic units into sectors or parts, a procedure that occurs in several contexts, such as political, health and school districting, social networks and sales territory or airspace assignment, to achieve some goal or to facilitate an activity. This presentation will focus on three main issues: Measures, a new approach to sectorization problems and an application in waste collection. When designing or comparing sectors different characteristics are usually taken into account. Some are commonly used, and they are related to the concepts of contiguity, equilibrium and compactness. These fundamental characteristics will be addressed, by defining new generic measures and by proposing a new measure, desirability, connected with the idea of preference. A new approach to sectorization inspired in Coulomb’s Law, which establishes a relation of force between electrically charged points, will be proposed. A charged point represents a small region with specific characteristics/values creating relations of attraction/repulsion with the others (two by two), proportional to the charges and inversely proportional to their distance. Finally, a real case about sectorization and vehicle routing in solid waste collection will be mentioned.