Tânia Ramos

Planning waste cooking oil collection systems.

This research has been motivated by a real-life problem of a waste cooking oil collection system characterized by the existence of multiple depots with an outsourced vehicle fleet, where the collection routes have to be plan. The routing problem addressed allows open routes between depots, i.e., all routes start at one depot but can end at the same or at a different one, depending on what minimizes the objective function considered. Such problem is referred as a Multi-Depot Vehicle Routing Problem with Mixed Closed and Open Inter-Depot Routes and is, in this paper, modeled through a mixed integer linear programming (MILP) formulation where capacity and duration constraints are taken into account. The model developed is applied to the real case study providing, as final results, the vehicle routes planning where a decrease of 13% on mileage and 11% on fleet hiring cost are achieved, when comparing with the current company solution.

“Identify-to-reject”: A specific strategy to avoid false memories in the DRM paradigm

Previous research using the Deese–Roediger–McDermott (DRM) paradigm has shown that lists of associates in which the critical words were easily identified as the themes of the lists produce lower levels of false memories in adults. In an attempt to analyze whether this effect is due to the application of a specific memory-editing process (the identify-to-reject strategy), two experiments manipulated variables that are likely to disrupt this strategy either at encoding or at retrieval. In Experiment 1, lists were presented at a very fast presentation rate to reduce the possibility of identifying the missing critical word as the theme of the list, and in Experiment 2, participants were pressed to give yes/no recognition answers within a very short time. The results showed that both of these manipulations disrupted the identifiability effect, indicating that the identify-to-reject strategy and theme identifiability play a major role in the rejection of false memories in the DRM paradigm.

Delimitation of service areas in reverse logistics networks with multiple depots

This paper describes a heuristic approach for the definition of service (or influence) areas of multiple depots in a reverse logistics network. This work is based on a case study: the recyclable waste collection system with 5 depots that covers seven municipalities in the Alentejo region, southern Portugal. The system optimization considers two objectives, related with economic and organizational issues: minimizing the variable costs (function of the travelled distances by the collection vehicles), and the pursuit of equity, aiming at minimizing the workload differences among depots. The goal of balancing workloads poses a problem not usually treated in the existing literature. This fact required the development of a new approach with innovative elements adjusted to the existing circumstances.

Planning Collection Routes with Multi-compartment Vehicles

This paper aims to assess the impact of using vehicles with multiple compartments in a recyclable waste collection system. Such systems perform single-material routes to collect three types of recyclable materials (paper, glass and plastic/metal), where vehicles with a single compartment are used. If vehicles with multi-compartments were used, two or even the three materials could be collected simultaneously without mixing them. A heuristic approach is developed to solve the multi-compartment vehicle routing problem and applied to a real waste collection system operating in Portugal.

The smart waste collection routing problem: Alternative operational management approaches

Abstract Waste collection is nowadays an increasingly important business. However, it is often an inefficient operation due to the high uncertainty associated with the real waste bins’ fill-levels. To deal with such uncertainty the use of sensors to transmit real time information is seen as possible solution. But, in order to improve operations’ efficiency, the sensors’ usage must be combined with optimization procedures that inform on the optimal collection routes to operationalize, so as to guarantee a maximization of the waste collected while also minimizing transportation costs. The present work explores this challenge and studies three operational management approaches to define dynamic optimal routes, considering the access to real-time information on the bins’ fill-levels. A real case study is solved and important results were found where significant profit improvements are observed when compared to the real operation. This shows the potential of the proposed approaches to build an expert system, which can support the operations managers decisions.

Waste Collection Planning Based on Real-Time Information

This paper studies the definition of dynamic routes regarding the waste collection problem. Based on access to real-time information, provided by sensors located at waste bin containers, a Vehicle Routing Problem with Profits (VRPP) solution approach is developed. This aims for the maximization of waste collected while minimizing the total distance travelled, resulting in a maximization of profit. Different scenarios are studied, based on real data. The conclusions clearly show that the usage of real-time information on containers fill-levels, coupled with an optimization approach to define dynamic routes potentially increases the profit of waste management companies.

Optimization of a Recyclable Waste Collection System - The Valorsul Case Study

This paper studies alternative scenarios for a recyclable waste collection system in order to increase efficiency in their operations. Three alternative scenarios are proposed where two different locations for one or two additional depots are studied. The problem is considered as a multi-depot vehicle routing problem and a solution approach is developed. The three scenarios are compared with the current solution regarding distance travelled, working hours, amount of waste collected and vehicle usage. Significant gains are obtained when depots are added to the current logistics system.

Inferential Costs of Trait Centrality in Impression Formation: Organization in Memory and Misremembering

An extension of the DRM paradigm was used to study the impact of central traits (Asch, 1946) in impression formation. Traits corresponding to the four clusters of the implicit theory of personality—intellectual, positive and negative; and social, positive and negative (Rosenberg et al., 1968)—were used to develop lists containing several traits of one cluster and one central trait prototypical of the opposite cluster. Participants engaging in impression formation relative to participants engaging in memorization not only produced higher levels of false memories corresponding to the same cluster of the list traits but, under response time pressure at retrieval, also produced more false memories of the cluster corresponding to the central trait. We argue that the importance of central traits stems from their ability to activate their corresponding semantic space within a specialized associative memory structure underlying the implicit theory of personality.