Guglielmo Lulli

• PhD in Operations Research
• Professor (Associate) at Lancaster University

This paper presents a Mixed Integer Programming model for optimal airspace sector design based on basic volume aggregation, focusing on workload balance and air traffic flow convexity. To overcome potential computational limitations, we develop a simple two-stage heuristic approach. The heuristic approach are evaluated using real-world traffic data...

In this paper, we present a novel data-driven optimization approach for trajectory-based air traffic flow management (ATFM). A key aspect of the proposed approach is the inclusion of airspace users’ trajectory preferences, which are computed from traffic data by combining clustering and classification techniques. Machine learning is also used to ex...

In this paper, we present a novel data-driven optimization approach for trajectory based air traffic flow management (ATFM). A key aspect of the proposed approach is the inclusion of airspace users' trajectory preferences, which are computed from traffic data by combining clustering and classification techniques. Machine learning is also used to ex...

Representing airspace users’ preferences in Air Traffic Flow Management (ATFM) mathematical models is becoming of high relevance. ATFM models aim to reduce congestion (en-route and at both departure and destination airports) and maximize the Air Traffic Management (ATM) system efficiency by determining the best trajectory for each aircraft. In this...

In this paper, we focus on designing efficient 4D trajectories for the planning phase of Air Traffic Flow Management (ATFM). A key feature of the proposed approach is the inclusion of stakeholders’ preferences and priorities. In particular, we have implemented two priority mechanisms recently developed by Eurocontrol, namely the Fleet Delay Reorder...

This paper presents an exhaustive study of the arrivals process at eight major European airports. Using inbound traffic data, we define, compare, and contrast a data-driven in-homogeneous Poisson and Pre-Scheduled Random Arrivals (PSRA) point process with respect to their ability to predict future demand. As part of this analysis, we show the weakn...

A key feature of trajectory based operations (TBO) – a new concept developed to modernize the air traffic system – is the inclusion of preferences and priorities of the air traffic management (ATM) stakeholders. In this paper, we present a new mathematical model to optimize flights’ 4D-trajectories. This is a multi-objective binary integer programm...

In this paper, we focus on designing efficient 4D trajectories for the planning phase of Air Traffic Flow Management (ATFM). A key feature of the proposed approach is the inclusion of stakeholders' preferences and priorities. In particular, as priority mechanisms we implemented fleet delay reordering and margins, two mechanisms recently developed b...

The Trajectory Based Operations (TBO) concept creates an environment for information sharing and collaborative decision making between the Air Traffic Management (ATM) stakeholders. This means that airspace users (AUs) share information about the intended 4D-trajectories of their flights, which are then negotiated with other stakeholders for a bett...

This paper presents an exhaustive study on the arrivals process at eight important European airports. Using inbound traffic data, we define, compare, and contrast a data-driven Poisson and PSRA point process. Although, there is sufficient evidence that the interarrivals might follow an exponential distribution, this finding does not directly transl...

The objective of this paper is to present a mathematical model that will contribute to the optimization and optimum configuration of the TBO concept. We develop a binary integer programming model whose aim is to assign a 4D-trajectory to each flight in order to optimize the efficiency of the ATM system. The model considers the preferred 4D-trajecto...

In this paper, we study a strategic fleet planning problem faced by TAP, the Portuguese legacy carrier. The study is intended to shed light on the aircraft models to select, as well as on the mix of aircraft to purchase (or financially lease) and the aircraft to operationally lease in order to cope with the forecasted passenger demand between Lisbo...

In this paper, we present the state-transition formulation for the unit commitment (UC) problem. This formulation uses new decision variables that capture the state transitions of the generators, instead of their on/off statuses. We show that this new approach produces a formulation which naturally includes valid inequalities, commonly used to stre...

We review some complexity results and present a viable heuristic approach based on the Variable Neighborhood Search (VNS) framework for multimode extension of combinatorial optimization problems, such as the the Set Covering Problem (SCP) and the Covering Location Problem (CLP).

In this paper we introduce the Multimode Covering Location Problem. This is a generalization of the Maximal Covering Location Problem that consists in locating a given number of facilities of different types with a limitation on the number of facilities sharing the same site. The problem is challenging and intrinsically much harder than its basic v...

The high cost of flight delays for airlines has motivated scientific research in air traffic flow management (ATFM). The majority of ATFM models in the literature are deterministic and do not take into account stochastic factors such as weather. In this paper, new stochastic programming models for ATFM are proposed. The models include as tactical c...

This paper presents two stochastic programming models for the allocation of time slots over a network of airports. The proposed models address three key issues. First, they provide an optimization tool to allocate time slots, which takes several operational aspects and airline preferences into account; second, they execute the process on a network...

This paper presents a binary optimization framework for modeling dynamic resource allocation problems. The framework (a) allows modeling flexibility by incorporating different objective functions, alternative sets of resources and fairness controls; (b) is widely applicable in a variety of problems in transportation, services and engineering; and (...

We present a model to describe the inbound air traffic over a congested hub and we show that this model gives a very accurate description of the traffic by comparing our theoretical distribution of the queue with the actual distribution observed at Heathrow airport. We also discuss the robustness of our model.

The Weighted Gene Regulatory Network (WGRN) problem consists in pruning a regulatory network obtained from DNA microarray gene expression data, in order to identify a reduced set of candidate elements which can explain the expression of all other genes. Since the problem appears to be particularly hard for general-purpose solvers, we develop a Gree...

Gene regulatory networks are a common tool to describe the chemical interactions between genes in a living cell. This paper considers the Weighted Gene Regulatory Network (WGRN) problem, which consists in identifying a reduced set of interesting candidate regulatory elements which can explain the expression of all other genes. We provide an integer...

This paper introduces the multi-mode set covering problem, which consists of a plurality of set covering problems linked by cardinality constraints. We propose a variable neighborhood search algorithm and a greedy randomized adaptive search procedure based on a common local search routine. This routine applies a penalized relaxation of the covering...

Aircraft operators need some flexibility when executing flight operations such as taking off, landing or entering into a sector, because the exact time of these operations is often affected by uncertainty. We express this flexibility in terms of time windows which are periods of time assigned to flights under the agreement that when a flight perfor...

The difficulty in synchronizing the activities of different actors and the existence of external constraints, e.g., weather conditions, usually produce some uncertainty on the exact time at which a flight operation can be executed. To cope with this uncertainty, aircraft operators need some flexibility when performing their flight operations, i.e.,...

In this paper, we present an aggregate mathematical model for air traffic flow management (ATFM), a problem of great concern both in Europe and in the United States. The model extends previous approaches by simultaneously taking into account three important issues: (i) the model explicitly incorporates uncertainty in the airport capacities; (ii) it...

In this paper, we present a case study on freight railway transportation in Italy, which is a by-product of research collaboration with a major Italian railway company. We highlight the main features of the Italian reality and propose a customized mathematical model to design the service network, that is, the set of origin-destination connections....

Nowadays, with the increasing need of traveling and flying, the air traffic system is highly capacity constrained due to the limited availability of resources. These resources are shared among the various domain actors. In this paper, we propose an architectural perspective for resource management in the aeronautic domain, which is based on resourc...

Airlines need to pay special attention to flights that may be liable to produce undesired downstream effects if subjected to delay. A mathematical formulation is proposed to identify these critical flights by defining a set of temporal intervals, called time window, which must be met during the flight execution. The width of the time window is vari...

The allocation of a limited number of resources among multiple self-interested stakeholders is a challenging issue for many real life systems and applications. Resource management for this type of systems is a challenging task because of the different objectives of the owner of the resources and the stakeholders. The owner aims to an efficient usag...

This paper presents a new integer programming (IP) model for large-scale instances of the air traffic flow management (ATFM) problem. The model covers all the phases of each flight—i.e., takeoff, en route cruising, and landing—and solves for an optimal combination of flow management actions, including ground-holding, rerouting, speed control, and a...

In this paper, we present a case study on freight railway transportation in Italy, which is a by-product of research collaboration with a major Italian railway company. We highlight the main features of the Italian reality and propose a customized mathematical model to design the service network, that is, the set of origin-destination connections....

Several causes of delay are deterring the air transportation system from being efficient. System capacity reductions are the major cause of delay. However, there are also some other causes, directly imputable to airlines, which may produce, in combination with the capacity reductions, undesired downstream effects. Therefore, with the purpose of con...

This paper defines a set of temporal intervals, called time windows, which are defined prior to flight departure and constitute milestones to be met during the flight execution. The size of the time windows is variable as it reflects all known constraints, such as punctuality at destination, runway capacities or congested en-route areas that the fl...

Biochemical networks are a particular kind of biological networks which describe the cell metabolism and regulate various biological functions, from biochemical pathways to cell growth. The relationship between structure, function and regulation in complex cellular networks is still a largely open question. This complexity calls for proper mathemat...

In this paper, we propose a methodology for making sense of large, multiple time-series data sets arising in expression analysis. Specifically, we present a mathematical model to release a reduced and coherent regulatory system given a putative regulatory network. We give two equivalent formulations of the problem and prove that the problem is NP-c...

This paper deals with the problem of finding equitable demand management strategies in congested systems with the presence of several classes of customers. Although the conclusions of the paper can be easily adapted to any market-based demand management philosophy, we mainly focus on congestion pricing, starting from a purely market-based economic...

This chapter is motivated by the study of a real-world application on blood delivery. The Austrian Red Cross (ARC), a non-profit organization, is in charge of delivering blood to hospitals on their request. To reduce their operating costs through higher flexibility, the ARC is interested in changing the policy of delivering blood products. Therefor...

In this paper, we present a new Integer Program (IP) for the Air Traffic Flow Management (ATFM) problem. The model we propose provides a complete representation of all the phases of each flights, i.e., the phase of taking-off, of cruising and of landing; suggesting all the actions to be implemented to achieve the goal of safe, efficient, and expedi...

In this paper a semi-online algorithm for scheduling multiprocessor tasks with partial information is proposed. We consider the case in which it is possible to exploit probabilistic information and use this information to obtain better solutions in comparison with standard non clairvoyant on-line algorithms. A wide computational analysis shows the...

In this paper, we study the multi-period TSP problem with stochastic urgent and regular demands. Urgent demands have to be satisfied immediately while regular demands can be satisfied either immediately or the day after. Demands appear stochastically at nodes. The objective is to minimize the average long-run delivery costs, knowing the probabiliti...

Air traffic flow management in Europe has to deal as much with capacity constraints in en route airspace as with the more usual capacity constraints at airports. The en route sector capacity constraints, in turn, generate complex interactions among traffic flows. We present a deterministic optimization model for the European air traffic flow manage...

One of the key factors for successful SOC-based systems is the ability to assure the achievement of Quality of Services. The knowledge and the enforcement of the Quality of Services allows for the definition of agreements that are the basis for any business process. In this paper we discuss a method for the evaluation of qualities associated with s...

In this paper, we propose a successive approximation heuristic which solves large stochastic mixed-integer programming problem with complete fixed recourse. We refer to this method as the Scenario Updating Method, since it solves the problem by considering only a subset of scenarios which is updated at each iteration. Only those scenarios which imp...

In this paper we study the stochastic batch sizing problems. We provide a unifying treatment of the problem, in which we formulate a multistage recourse problem as well as a probabilistically constrained problem. The solution approach that we adopt for these problems may be classified as a branch and price (B&P) method. Through our computational ex...

In this paper, we present a mathematical model to design the service network, that is the set of origin-destination connections. The resulting model considers both full and empty freight car movements, and takes into account handling costs. More specifically, the model suggests the services to provide, as well as the number of trains and the number...

This paper has been motivated by the study of a real application, the transshipment container terminal of Gioia Tauro in Italy. The activities in a container terminal concern with the movement of containers from/to mother vessels and feeders and with the handling and storage of containers in the yard. For such type of applications both operational...

This paper has been motivated by the study of a real application, the transshipment container terminal of Gioia Tauro in Italy. The activities in a container terminal concern with the movement of containers from/to mother vessels and feeders and with the handling and storage of containers in the yard. For such type of applications both operational...

In this paper, we present a branch-and-price method to solve special structured multistage stochastic integer programming problems. We validate our method on two different versions of a multistage stochastic batch-sizing problem (SBSP). One version adopts a recourse formulation, and the other is based on probabilistic constraints. Our algorithmic a...

The Ground Delay Program (GDP) is an air tra卤c flow management mech-anism used to decrease the rate of in-coming flights into an airport when it is projected that arrival demand will exceed capacity. Under a GDP, a set of flights destined for a single airport is assigned ground delays. In this paper we investigate how the set of flights to which de...

In most of the optimization models developed to manage airports operations, arrivals and departures capacities are treated as independent variables: that is the number of flights allowed to take off does not affect the number of landings in any unit of time, and vice versa. This assumption is seldom verified in most of the congested airports, where...

We describe a new two-level hierarchical architecture for air traffic management problems with corresponding mathematical models. The first level represents the air route network, and its solutions provide the air traffic flows on each arc of the network. This level interacts with the second one, which represents the single airway and its own air t...

We propose an approximation scheme to solve large stochastic mixed-integer programming problems with fixed recourse. We refer to this as the scenario updating method. The algorithm is based on solving instances of the problem, which contain only a subset of the scenarios in the scenario tree. At each iteration, the subset of scenarios is updated by...

In this chapter, we present the airport capacity allocation problem, i.e., the problem of finding for each time unit the optimal balance between the number of arrivals and departures in order to reduce the total economic loss over a given decision horizon. In this class of problem, airport capacity is represented by an arrival-departure capacity cu...

In this paper we present a branch-and-price method to solve special structured multi-stage stochastic integer programming problems. We validate our method on two different versions of a multi-stage stochastic batch-sizing problem. One version adopts a recourse formulation, and the other is based on probabilistic constraints. Our algorithmic approac...

Predicting behavior of large-scale biochemical networks represents one of the greatest chal- lenges in bio-informatics and computational biology. The relationship between structure, function and regulation is a still largely open question. Herein, we focus on the prediction of genotype-phenotype relationships from experimental data. A gene regulato...