Johan Springael

PROMETHEE and AHP: The design of operational synergies in multicriteria analysis.: Strengthening PROMETHEE with ideas of AHP

Abstract This paper discusses the strengths and weaknesses of the Preference Ranking Organisation MeTHod for Enrichment Evaluations (PROMETHEE) and analytic hierarchy process (AHP) methods. Building upon this analysis, recommendations are formulated to integrate into PROMETHEE a number of useful AHP features, especially as regards the design of the decision-making hierarchy (ordering of goals, sub-goals, dimensions, criteria, projects, etc.) and the determination of weights. As a result of mixing basis features of both methods, operational synergies can be achieved in MCA.

A metaheuristic for the school bus routing problem with bus stop selection

Existing literature on routing of school buses has focused mainly on building intricate models that attempt to capture as many real-life constraints and objectives as possible. In contrast, the focus of this paper is on understanding the joint problem of bus route generation and bus stop selection – two important sub-problems – in its most basic form. To this end, this paper defines the school bus routing problem (SBRP) as a variant of the vehicle routing problem in which three simultaneous decisions have to be made: (1) determine the set of stops to visit, (2) determine for each student which stop (s)he should walk to, and (3) determine routes that lie along the chosen stops, so that the total traveled distance is minimized. An MIP model of this basic problem is developed.

The zero-emission certificates: A novel CO2-pollution reduction instrument applied to the electricity market

Abstract Today several instruments exist to decrease air pollution. The paper discusses pollution taxes, emission trading permits and green certificates applied to reduce the CO 2 -emissions in the electricity sector. It then investigates how the different mechanisms behind these three instruments can possibly be combined. The proposed approach is to introduce the concept of zero-emission certificates (ZEC). ZEC are confirming actual emission reductions achieved by electricity producers as compared to a well-defined baseline. Producers can trade ZEC on a market to achieve least-cost efficiency in their reduction efforts. Distributors can themselves produce an additional contribution to emission-reductions by decreasing the final demand, i.e., by producing zero-emission MWh. In this way the electricity market is approached from both the supply and the demand sides. The paper uses system dynamics to validate the approach. It shows why it is in the interest of all operators to make the largest possible reduction efforts as long as they are compatible with economic efficiency.

Construction of Bäcklund Transformations with Binary Bell Polynomials

A method for constructing Backlund transformations (BTs) for sech-squared soliton systems is presented as an alternative to the usual procedure based on the bilinear exchange formalism. It is shown to work without the need of a bilinear representation in the case of a nonlocal Boussinesq equation. The obtained bilinear BT produces a modified nonlocal Boussinesq equation.

MISTRAL : a game-theoretical model to allocate security measures in a multi-modal chemical transportation network with adaptive adversaries

In this paper we present a multi-modal security-transportation model to allocate security resources within a chemical supply chain which is characterized by the use of different transport modes, each having their own security features. We consider security-related risks so as to take measures against terrorist acts which could target critical transportation systems. The idea of addressing security-related issues, by supporting decisions for preventing or mitigating intentional acts on transportation infrastructure, has gained attention in academic research only recently. The decision model presented in this paper is based on game theory and it can be employed to organize intelligence capabilities aimed at securing chemical supply chains. It enables detection and warning against impending attacks on transportation infrastructures and the subsequent adoption of security countermeasures. This is of extreme importance for preventing terrorist attacks and for avoiding (possibly huge) human and economic losses. In our work we also provide data sources and numerical simulations by applying the proposed model to a illustrative multi-modal chemical supply chain.

On the Hirota Representation of Soliton Equations with One Tau-Function

Alternative Hirota representations in terms of a single tau-function are derived for a variety of soliton equations, including the sine-Gordon and the Tzitzeica equations. The relevance of these representations with respect to known bilinear representations of integrable hierarchies is briefly discussed. The essentials of the derivation method are presented.

Metaheuristics for the risk-constrained cash-in-transit vehicle routing problem

This paper proposes a variant of the well-known capacitated vehicle routing problem that models the routing of vehicles in the cash-in-transit industry by introducing a risk constraint. In the Risk-constrained Cash-in-Transit Vehicle Routing Problem (RCTVRP), the risk of being robbed, which is assumed to be proportional both to the amount of cash being carried and the time or the distance covered by the vehicle carrying the cash, is limited by a risk threshold. A library containing two sets of instances for the RCTVRP, some with known optimal solution, is generated. A mathematical formulation is developed and small instances of the problem are solved by using IBM CPLEX. Four constructive heuristics as well as a local search block composed of six local search operators are developed and combined using two different metaheuristic structures: a multistart heuristic and a perturb-and-improve structure. In a statistical experiment, the best parameter settings for each component are determined, and the resulting heuristic configurations are compared in their best possible setting. The resulting metaheuristics are able to obtain solutions of excellent quality in very limited computing times.

The k-dissimilar vehicle routing problem

In this paper we define a new problem, the aim of which is to find a set of k dissimilar solutions for a vehicle routing problem (VRP) on a single instance. This problem has several practical applications in the cash-in-transit sector and in the transportation of hazardous materials. A min–max mathematical formulation is proposed which requires a maximum similarity threshold between VRP solutions, and the number k of dissimilar VRP solutions that need to be generated. An index to measure similarities between VRP solutions is defined based on the edges shared between pairs of alternative solutions. An iterative metaheuristic to generate k dissimilar alternative solutions is also presented. The solution approach is tested using large and medium size benchmark instances for the capacitated vehicle routing problem.

A large neighbourhood metaheuristic for the risk-constrained cash-in-transit vehicle routing problem

In this paper, we propose a new metaheuristic to solve the Risk constrained Cash-in-Transit Vehicle Routing Problem (Rctvrp). The Rctvrp is a variant of the well-known capacitated vehicle routing problem and models the problem of routing vehicles in the cash-in-transit sector. In the Rctvrp, the risk associated with a robbery represents a critical aspect that is treated as a limiting factor subject to a maximum risk threshold.A new metaheuristic, called aco-lns is developed. It combines the ant colony heuristic for the travelling salesman problem and a variable neighbourhood descent within an large neighbourhood search framework.A new library of Rctvrp instances with known optimal solutions is proposed. The aco-lns is extensively tested on small, medium and large benchmark instances and compared with all existing solution approaches for the Rctvrp. HighlightsA new metaheuristic named ACO-LNS is developed to increase security in the CIT sector.The ACO-LNS combines the ant colony optimization with a VND heuristic.The ACO-LNS uses an effective large neighbourhood search heuristic.A set of benchmark instances for the RCTVRP is proposed and made publicly available.The ACO-LNS outperforms the existing algorithms for the RCTVRP.

Simulation d'un marché de certificats verts pour la promotion de l'énergie éolienne EN Belgique

Abstract Renewable sources used for the generation of electricity have today quite high production costs in Europe. The liberalisation of the electricity market makes their advancement still more difficult, as it is expected to exert pressures towards lower prices. There are however strong arguments supporting renewable electricity. First, it is highly recommended to preserve the non-renewable fossil natural resources. Second, the use of renewable resources reduces the emissions of CO2 considered as being the most important greenhouse gas. In Belgium the most promising renewable production source for electricity is wind energy. Suitable policies shall amplify a virtuous cycle rendering this type of production competitive with fossil sources on a short-time basis. The present paper presents a simulation with system dynamics of a supporting policy based on the creation of a green-certificate market. The objective of the study is to demonstrate the feasibility of this approach, and to provide to regulators a decision tool for properly designing the main policy parameters as necessary conditions for its success.