Jesper Larsen | Technical University of Denmark (DTU) (original) (raw)

Papers by Jesper Larsen

Journal of Air Transport Management, 2007

Over the past decade, airlines have become more concerned with developing an optimal flight sched... more Over the past decade, airlines have become more concerned with developing an optimal flight schedule, with very little slack left to accommodate for any form of variation from the optimal solution. During operation the planned schedules often have to be revised due to disruptions caused by for example severe weather, technical problems and crew sickness. Thus, the field of Airline Disruption Management has emerged within the past few years. The increased focus on cutting cost at the major airlines has intensified the interest in the development of new and cost efficient methods to handle airline disruptions.

Computers & Operations Research, 2010

The airline industry is notably one of the success stories with respect to the use of optimizatio... more The airline industry is notably one of the success stories with respect to the use of optimization based methods and tools in planning. Both in planning of the assignment of available aircraft to flights and in crew scheduling, these methods play a major role.

Computers & Operations Research, 2006

In this chapter we discuss the Vehicle Routing Problem with Time Windows in terms of its mathemat... more In this chapter we discuss the Vehicle Routing Problem with Time Windows in terms of its mathematical modeling, its structure and decomposition alternatives. We then present the master problem and the subproblem for the column generation approach, respectively. Next, we illustrate a branch-and-bound framework and address acceleration strategies used to increase the efficiency of branch-and-price methods. Then, we describe generalizations of the problem and report computational results for the classic Solomon test sets. Finally, we present our conclusions and discuss some open problems.

Abstract. The Home Care Crew Scheduling Problem emerges in modern healthcare systems. The idea of... more Abstract. The Home Care Crew Scheduling Problem emerges in modern healthcare systems. The idea of home care is to offer a variety of services in the homes of the patients, whenever this is possible. A number of nurses and other personnel go from home to home and provide the necessary service. The Home Care Crew Scheduling Problem deals with the assignment of visits to caretakers and the scheduling of the visits. The objective of the mathematical optimization is to provide a higher level of service at a reduced cost.

Abstract The performance of the auction algorithms for the shortest paths has been investigated i... more Abstract The performance of the auction algorithms for the shortest paths has been investigated in four papers with di ering conclusions. In the following I report a series of experiments with the code from the two most recent papers. The experiments clearly show that the auction algorithm is inferior to state-of-theart shortest paths algorithms Keywords: shortest path problem, auction algorithm, performance results.

Page 1. 1 Jesper Larsen & Jens Clausen Informatics and Mathematical Modelling / Operations Resear... more Page 1. 1 Jesper Larsen & Jens Clausen Informatics and Mathematical Modelling / Operations Research The Max Flow Problem Jesper Larsen & Jens Clausen jla,jc@imm.dtu.dk Informatics and Mathematical Modelling Technical University of Denmark Page 2. 2 Jesper Larsen & Jens Clausen Informatics and Mathematical Modelling / Operations Research 2 3 4 5 6 6 3 6 3 6 3 1 2 1 2 8 4 2 1 3 4 7 r s 1 Page 3.

A series of data assimilation experiments has been performed to investigate the impact of satelli... more A series of data assimilation experiments has been performed to investigate the impact of satellite SST data on ocean hindcasts in the North Sea-Baltic Sea region. She and Høyer (2004) has shown that the effective number of in-situ observations is comparable to the effective number of satellite observations. By effective observations we mean observations gridded to spatial and temporal scales of physical relevance in order to reduce redundancy. The impact of including in-situ SST observations has therefore also been investigated.

Since the deregulation of many markets, airlines have become more concerned with developing an op... more Since the deregulation of many markets, airlines have become more concerned with developing an optimal flight schedule, allowing little slack to accommodate variations from the optimal solution. During operation, the planned schedules often have to be revised because of disruptions caused by severe weather, technical problems and crew sickness. Thus, airline disruption management techniques have emerged.

In this chapter we discuss the Vehicle Routing Problem with Time Windows in terms of its mathemat... more In this chapter we discuss the Vehicle Routing Problem with Time Windows in terms of its mathematical modeling, its structure and decomposition alternatives. We then present the master problem and the subproblem for the column generation approach, respectively. Next, we illustrate a branch-and-bound framework and address acceleration strategies used to increase the efficiency of branch-and-price methods. Then, we describe generalizations of the problem and report computational results for the classic Solomon test sets.

Abstract The signal controllers of heavy-traffic arteries are subject to optimization to best acc... more Abstract The signal controllers of heavy-traffic arteries are subject to optimization to best accomodate the movement of the large traffic volumes. The DOGS system for arterial optimization works by adjusting the common cycle time according to detected traffic conditions and was tested in the vissim microsimulator for a section of the Danish ringroad 3.

Abstract In this paper we consider an important problem for the airline industry. The widely stud... more Abstract In this paper we consider an important problem for the airline industry. The widely studied crew pairing problem is typically formulated as a set partitioning problem and solved using the branchand-price methodology. Here we develop a new integer programming framework, based on the concept of subsequence generation, for solving the set partitioning formulation. In subsequence generation one restricts the number of permitted subsequent flights, that a crew member can turn to after completing any particular flight.

Summary This thesis investigates the possibilities in applying Operations Research (OR) to autono... more Summary This thesis investigates the possibilities in applying Operations Research (OR) to autonomous vehicular traffic. The explicit difference to most other research today is that we presume that an agent is present in every vehicle–hence Agent Based Individual Traffic guidance (ABIT).

This paper considers the dynamic multi-period vehicle routing problem which deals with the distri... more This paper considers the dynamic multi-period vehicle routing problem which deals with the distribution of orders from a depot to a set of customers over a multi-period time horizon. Customer orders and their feasible service periods are dynamically revealed over time. The objectives are to minimize total travel costs and customer waiting, and to balance the daily workload over the planning horizon. This problem originates from a large distributor operating in Sweden.

Using Heuristics to Solve the Dedicated Aircraft Recovery Problem. Michael Løve, Kim Riis Sørense... more Using Heuristics to Solve the Dedicated Aircraft Recovery Problem. Michael Løve, Kim Riis Sørensen, Jesper Larsen, Jens Clausen. Keywords, Disruption Management, Optimization, Airline Planning, Dedicated Aircraft Recovery, Heuristics, Irregular operations. Type, Journal paper [With referee]. Journal, Central European Journal of Operations Research. Year, 2005 Month June Vol. 13 No. 2 pp. 189-207. ISBN / ISSN, 1435-246X. BibTeX data, [bibtex]. IMM Group(s), Operations Research. Back :: IMM Publications.

Abstract An ontology is a classification model for a given domain. In information retrieval, onto... more Abstract An ontology is a classification model for a given domain. In information retrieval, ontologies are used to perform broad searches. An ontology can be visualized as nodes and edges. Each node represents an element and each edge a relation between a parent and a child element. Working with an ontology becomes easier with a visual representation. An idea is to use the expressive power of 3D representation to provide visualization for the user.

Journal of Air Transport Management, 2007

Over the past decade, airlines have become more concerned with developing an optimal flight sched... more Over the past decade, airlines have become more concerned with developing an optimal flight schedule, with very little slack left to accommodate for any form of variation from the optimal solution. During operation the planned schedules often have to be revised due to disruptions caused by for example severe weather, technical problems and crew sickness. Thus, the field of Airline Disruption Management has emerged within the past few years. The increased focus on cutting cost at the major airlines has intensified the interest in the development of new and cost efficient methods to handle airline disruptions.

Computers & Operations Research, 2010

The airline industry is notably one of the success stories with respect to the use of optimizatio... more The airline industry is notably one of the success stories with respect to the use of optimization based methods and tools in planning. Both in planning of the assignment of available aircraft to flights and in crew scheduling, these methods play a major role.

Computers & Operations Research, 2006

In this chapter we discuss the Vehicle Routing Problem with Time Windows in terms of its mathemat... more In this chapter we discuss the Vehicle Routing Problem with Time Windows in terms of its mathematical modeling, its structure and decomposition alternatives. We then present the master problem and the subproblem for the column generation approach, respectively. Next, we illustrate a branch-and-bound framework and address acceleration strategies used to increase the efficiency of branch-and-price methods. Then, we describe generalizations of the problem and report computational results for the classic Solomon test sets. Finally, we present our conclusions and discuss some open problems.

Abstract. The Home Care Crew Scheduling Problem emerges in modern healthcare systems. The idea of... more Abstract. The Home Care Crew Scheduling Problem emerges in modern healthcare systems. The idea of home care is to offer a variety of services in the homes of the patients, whenever this is possible. A number of nurses and other personnel go from home to home and provide the necessary service. The Home Care Crew Scheduling Problem deals with the assignment of visits to caretakers and the scheduling of the visits. The objective of the mathematical optimization is to provide a higher level of service at a reduced cost.

Abstract The performance of the auction algorithms for the shortest paths has been investigated i... more Abstract The performance of the auction algorithms for the shortest paths has been investigated in four papers with di ering conclusions. In the following I report a series of experiments with the code from the two most recent papers. The experiments clearly show that the auction algorithm is inferior to state-of-theart shortest paths algorithms Keywords: shortest path problem, auction algorithm, performance results.

Page 1. 1 Jesper Larsen & Jens Clausen Informatics and Mathematical Modelling / Operations Resear... more Page 1. 1 Jesper Larsen & Jens Clausen Informatics and Mathematical Modelling / Operations Research The Max Flow Problem Jesper Larsen & Jens Clausen jla,jc@imm.dtu.dk Informatics and Mathematical Modelling Technical University of Denmark Page 2. 2 Jesper Larsen & Jens Clausen Informatics and Mathematical Modelling / Operations Research 2 3 4 5 6 6 3 6 3 6 3 1 2 1 2 8 4 2 1 3 4 7 r s 1 Page 3.

A series of data assimilation experiments has been performed to investigate the impact of satelli... more A series of data assimilation experiments has been performed to investigate the impact of satellite SST data on ocean hindcasts in the North Sea-Baltic Sea region. She and Høyer (2004) has shown that the effective number of in-situ observations is comparable to the effective number of satellite observations. By effective observations we mean observations gridded to spatial and temporal scales of physical relevance in order to reduce redundancy. The impact of including in-situ SST observations has therefore also been investigated.

Since the deregulation of many markets, airlines have become more concerned with developing an op... more Since the deregulation of many markets, airlines have become more concerned with developing an optimal flight schedule, allowing little slack to accommodate variations from the optimal solution. During operation, the planned schedules often have to be revised because of disruptions caused by severe weather, technical problems and crew sickness. Thus, airline disruption management techniques have emerged.

In this chapter we discuss the Vehicle Routing Problem with Time Windows in terms of its mathemat... more In this chapter we discuss the Vehicle Routing Problem with Time Windows in terms of its mathematical modeling, its structure and decomposition alternatives. We then present the master problem and the subproblem for the column generation approach, respectively. Next, we illustrate a branch-and-bound framework and address acceleration strategies used to increase the efficiency of branch-and-price methods. Then, we describe generalizations of the problem and report computational results for the classic Solomon test sets.

Abstract The signal controllers of heavy-traffic arteries are subject to optimization to best acc... more Abstract The signal controllers of heavy-traffic arteries are subject to optimization to best accomodate the movement of the large traffic volumes. The DOGS system for arterial optimization works by adjusting the common cycle time according to detected traffic conditions and was tested in the vissim microsimulator for a section of the Danish ringroad 3.

Abstract In this paper we consider an important problem for the airline industry. The widely stud... more Abstract In this paper we consider an important problem for the airline industry. The widely studied crew pairing problem is typically formulated as a set partitioning problem and solved using the branchand-price methodology. Here we develop a new integer programming framework, based on the concept of subsequence generation, for solving the set partitioning formulation. In subsequence generation one restricts the number of permitted subsequent flights, that a crew member can turn to after completing any particular flight.

Summary This thesis investigates the possibilities in applying Operations Research (OR) to autono... more Summary This thesis investigates the possibilities in applying Operations Research (OR) to autonomous vehicular traffic. The explicit difference to most other research today is that we presume that an agent is present in every vehicle–hence Agent Based Individual Traffic guidance (ABIT).

This paper considers the dynamic multi-period vehicle routing problem which deals with the distri... more This paper considers the dynamic multi-period vehicle routing problem which deals with the distribution of orders from a depot to a set of customers over a multi-period time horizon. Customer orders and their feasible service periods are dynamically revealed over time. The objectives are to minimize total travel costs and customer waiting, and to balance the daily workload over the planning horizon. This problem originates from a large distributor operating in Sweden.

Using Heuristics to Solve the Dedicated Aircraft Recovery Problem. Michael Løve, Kim Riis Sørense... more Using Heuristics to Solve the Dedicated Aircraft Recovery Problem. Michael Løve, Kim Riis Sørensen, Jesper Larsen, Jens Clausen. Keywords, Disruption Management, Optimization, Airline Planning, Dedicated Aircraft Recovery, Heuristics, Irregular operations. Type, Journal paper [With referee]. Journal, Central European Journal of Operations Research. Year, 2005 Month June Vol. 13 No. 2 pp. 189-207. ISBN / ISSN, 1435-246X. BibTeX data, [bibtex]. IMM Group(s), Operations Research. Back :: IMM Publications.

Abstract An ontology is a classification model for a given domain. In information retrieval, onto... more Abstract An ontology is a classification model for a given domain. In information retrieval, ontologies are used to perform broad searches. An ontology can be visualized as nodes and edges. Each node represents an element and each edge a relation between a parent and a child element. Working with an ontology becomes easier with a visual representation. An idea is to use the expressive power of 3D representation to provide visualization for the user.