- Department of Management Engineering, Building 426, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
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Research Interests:
Research Interests:
Research Interests:
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... 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.
Research Interests:
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... 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 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... 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 Research The Max Flow Problem Jesper Larsen & Jens Clausen jla,jc@imm.dtu.dk Informatics and Mathematical Modelling Technical University of Denmark... 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 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... 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 optimal flight schedule, allowing little slack to accommodate variations from the optimal solution. During operation, the planned schedules... 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 mathematical modeling, its structure and decomposition alternatives. We then present the master problem and the subproblem for the column generation... 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 accomodate the movement of the large traffic volumes. The DOGS system for arterial optimization works by adjusting the common cycle time... 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 studied crew pairing problem is typically formulated as a set partitioning problem and solved using the branchand-price methodology. Here we... 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 autonomous vehicular traffic. The explicit difference to most other research today is that we presume that an agent is present in every... 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 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... 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 Sørensen, Jesper Larsen, Jens Clausen. Keywords, Disruption Management, Optimization, Airline Planning, Dedicated Aircraft Recovery, Heuristics,... 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, 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... 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.
Multilocus sequence typing (MLST) is a sequence-based geno-typing method based on polymorphisms (each variant is termed an allele) in seven housekeeping genes (loci)(arcC, aroE, glpF, gmk, pta, tpi, and yqiL) in Staphylococcus aureus... more
Multilocus sequence typing (MLST) is a sequence-based geno-typing method based on polymorphisms (each variant is termed an allele) in seven housekeeping genes (loci)(arcC, aroE, glpF, gmk, pta, tpi, and yqiL) in Staphylococcus aureus providing unique allelic profiles known as sequence types (STs)(1). The data obtained by MLST are highly reproducible and are available in the S. aureus MLST database (http://saureus. mlst. net/).
In this paper we consider the problem of allocating arriving ships to discrete berth locations at container terminals. This problem is recognized as one of the most important processes for any container terminal. We review and describe... more
In this paper we consider the problem of allocating arriving ships to discrete berth locations at container terminals. This problem is recognized as one of the most important processes for any container terminal. We review and describe three main models of the discrete dynamic berth allocation problem, improve the performance of one model, and, through extensive numerical tests, compare all models from a computational perspective. The results indicate that a generalized set-partitioning model outperforms all other existing models.
Abstract This paper addresses the Ground Crew Rostering Problem with Work Patterns, an important manpower planning problem arising in the ground operations of airline companies. We present a cutting stock-based integer programming... more
Abstract This paper addresses the Ground Crew Rostering Problem with Work Patterns, an important manpower planning problem arising in the ground operations of airline companies. We present a cutting stock-based integer programming formulation of the problem and describe a powerful heuristic decomposition approach, which utilizes column generation and variable fixing, to construct efficient rosters for a six-month time horizon.
Summary Real-time recovery is receiving a fast growing interest in an increasingly competitive railway operation market. This thesis considers the area of rolling stock dispatching which is one of the typical real-time railway dispatching... more
Summary Real-time recovery is receiving a fast growing interest in an increasingly competitive railway operation market. This thesis considers the area of rolling stock dispatching which is one of the typical real-time railway dispatching problems. All work of the thesis is based on the network and planning processes of the railway operator DSB S-tog a/s.
Background Methicillin-resistant Staphylococcus aureus (MRSA) is an important nosocomial and community-associated pathogen. Recently, livestock-associated MRSA (LA-MRSA) has emerged and disseminated in Europe and North America and now... more
Background Methicillin-resistant Staphylococcus aureus (MRSA) is an important nosocomial and community-associated pathogen. Recently, livestock-associated MRSA (LA-MRSA) has emerged and disseminated in Europe and North America and now constitutes a considerable zoonotic burden in humans with risk factors of pig exposure, whereas the extent of the livestock reservoir is relatively unknown on other continents.
This report is an update and extension of the DMI Technical Report No. 99-20: Laursen, Ellen Vaarby, Jesper Larsen, Kirsten Rajakumar, John Cappelen and Torben Schmith, 1999. Observed Daily Precipitation & Temperature from Six Danish... more
This report is an update and extension of the DMI Technical Report No. 99-20: Laursen, Ellen Vaarby, Jesper Larsen, Kirsten Rajakumar, John Cappelen and Torben Schmith, 1999. Observed Daily Precipitation & Temperature from Six Danish Sites, 1874-2000. The update and extension consist of
To the Editor: Enterococcus faecalis, which exists commensally in the gut in warm-blooded animals and humans, is an opportunistic pathogen that causes a variety of community-acquired and health care–associated infections, such as urinary... more
To the Editor: Enterococcus faecalis, which exists commensally in the gut in warm-blooded animals and humans, is an opportunistic pathogen that causes a variety of community-acquired and health care–associated infections, such as urinary tract and intraabdominal infections, bacteremia, and endocarditis (1). Only a few studies have assessed the relationships between clinical E. faecalis strains; strains endemic to the health care setting; and community strains residing in humans, animals, or animal-origin food (2).
This paper discusses the major issues in operational three dimensional (3D) ocean modelling for the Baltic Sea, based on the experiences in DMI Centre for Ocean and Ice in recent years. Both scientific and technical aspects of the... more
This paper discusses the major issues in operational three dimensional (3D) ocean modelling for the Baltic Sea, based on the experiences in DMI Centre for Ocean and Ice in recent years. Both scientific and technical aspects of the operational ocean modelling are discussed. Recommendations are given to the development of the Baltic Sea operational 3D ocean models. Key words: the Baltic Sea, 3D Ocean modelling
Abstract. This paper presents a simulation model to study the robustness of timetables of DSB S-tog a/s, the city rail of Copenhagen. Dealing with rush hour scenarios only, the simulation model investigates the effects of disturbances on... more
Abstract. This paper presents a simulation model to study the robustness of timetables of DSB S-tog a/s, the city rail of Copenhagen. Dealing with rush hour scenarios only, the simulation model investigates the effects of disturbances on the S-tog network. Several timetables are analyzed with respect to robustness. Some of these are used in operation and some are generated for the purpose of investigating timetables with specific alternative characteristics.
A high quality fine resolution bathymetry data set has long been a priority for operational ocean modelers. Currently ten bathymetry data sets covering different parts of the North European Shelf Sea area are available at DMI. These data... more
A high quality fine resolution bathymetry data set has long been a priority for operational ocean modelers. Currently ten bathymetry data sets covering different parts of the North European Shelf Sea area are available at DMI. These data sets have different coverage, resolution, and accuracy in different areas (a detailed description follows in Section 2).
Abstract Efficiently coordinating the movement of trains on a railway network is a central part of the planning process for a railway company. This paper reviews models and methods that have been proposed in the literature to assist... more
Abstract Efficiently coordinating the movement of trains on a railway network is a central part of the planning process for a railway company. This paper reviews models and methods that have been proposed in the literature to assist planners in finding train routes. Since the problem of routing trains on a railway network entails allocating the track capacity of the network (or part thereof) over time in a conflict-free manner, all studies that model railway track allocation in some capacity are considered relevant.
Livestock-associated meticillin-resistant Staphylococcus aureus belonging to clonal complex 398 (LA-MRSA CC398) is an important cause of zoonotic infections in several countries, but there is only a single published report of this lineage... more
Livestock-associated meticillin-resistant Staphylococcus aureus belonging to clonal complex 398 (LA-MRSA CC398) is an important cause of zoonotic infections in several countries, but there is only a single published report of this lineage from the United Kingdom (UK). Here, we describe the isolation of LA-MRSA CC398 from bulk tank milk from five geographically dispersed farms in the UK. Our findings suggest that LA-MRSA CC398 is established in livestock in the UK.
Abstract A tramp ship operator typically has some contracted cargoes that must be carried and seeks to maximize profit by carrying optional cargoes. Hence, tramp ships operate much like taxies following available cargoes and not according... more
Abstract A tramp ship operator typically has some contracted cargoes that must be carried and seeks to maximize profit by carrying optional cargoes. Hence, tramp ships operate much like taxies following available cargoes and not according to a fixed route network and itinerary as liner ships. Marine fuel is referred to as bunker and bunker costs constitute a significant part of the daily operating costs. There can be great variations in bunker prices across bunker ports so it is important to carefully plan bunkering for each ship.
This document is an appendix to the paper entitled" A parallel matheuristic for the Technician Routing and Scheduling Problem". The Technician Routing and Scheduling Problem (TRSP) consists in routing staff to serve requests for service,... more
This document is an appendix to the paper entitled" A parallel matheuristic for the Technician Routing and Scheduling Problem". The Technician Routing and Scheduling Problem (TRSP) consists in routing staff to serve requests for service, taking into account time windows, skills, tools, and spare parts. The TRSP extends the Vehicle Routing Problem with Time Windows (VRPTW).
Abstract The problem of routing trains through railway junctions is an integral part of railway operations. Large junctions are highly interconnected networks of track where multiple railway lines meet, intersect, and split. The number of... more
Abstract The problem of routing trains through railway junctions is an integral part of railway operations. Large junctions are highly interconnected networks of track where multiple railway lines meet, intersect, and split. The number of possible routings makes this a very complicated problem. Here we show how the problem can be formulated as a set packing model.
Increased focus on the analysis and modelling of climatic change and the related analysis of observed climatic data calls for long time series of climate data. Until recently many studies have been based on annual and monthly values. But... more
Increased focus on the analysis and modelling of climatic change and the related analysis of observed climatic data calls for long time series of climate data. Until recently many studies have been based on annual and monthly values. But many climatic extreme events with great impact on Society, eg maximum precipitation in 24 hours, may be hidden by the aggregation into monthly or annual values.
Summary The microtubule (MT) plus-end-tracking protein EB1 is required for assembly of primary cilia in mouse fibroblasts, but the mechanisms involved and the roles of the related proteins EB2 and EB3 in ciliogenesis are unknown. Using... more
Summary The microtubule (MT) plus-end-tracking protein EB1 is required for assembly of primary cilia in mouse fibroblasts, but the mechanisms involved and the roles of the related proteins EB2 and EB3 in ciliogenesis are unknown. Using protein depletion experiments and expression of dominant-negative constructs we show here that EB1 and EB3, but not EB2, are required for assembly of primary cilia in cultured cells.
Abstract The aim of this project is to explore a possible two-phase approach in solving routing problems in the homecare sector. The idea behind the two-phase approach is first to divide all visits in a number of clusters based on... more
Abstract The aim of this project is to explore a possible two-phase approach in solving routing problems in the homecare sector. The idea behind the two-phase approach is first to divide all visits in a number of clusters based on geographical location, preferences, home care worker skills, joint visits etc. Every cluster is associated with one home care worker.
Abstract The unique institutional environment of China‟ s stock markets provides a rich setting to study the relationship between investors‟ behavior and market returns in the case of information inefficiency. This study extends the well... more
Abstract The unique institutional environment of China‟ s stock markets provides a rich setting to study the relationship between investors‟ behavior and market returns in the case of information inefficiency. This study extends the well documented Dogs of the Dow (Dow Dogs) strategy to China‟ s A share stock market. We find that Dow Dogs portfolios significantly outperform the market benchmark for the period of 1994 to 2009 in China‟ s markets.
Abstract In this paper we present a new scheduling problem and describe a shortest path based heuristic as well as a dynamic programming based exact optimization algorithm to solve it. The Selective Multi-Category Parallel-Servicing... more
Abstract In this paper we present a new scheduling problem and describe a shortest path based heuristic as well as a dynamic programming based exact optimization algorithm to solve it. The Selective Multi-Category Parallel-Servicing Problem (SMCPSP) arises when a set of jobs has to be scheduled on a server (machine) with limited capacity. Each job requests service in a prespecified time window and belongs to a certain category.
Abstract The auction approach for the shortest path problem as introduced by Bertsekas is tested experimentally. Parallel algorithms using the auction approach are developed and tested. Both the sequential and parallel auction algorithms... more
Abstract The auction approach for the shortest path problem as introduced by Bertsekas is tested experimentally. Parallel algorithms using the auction approach are developed and tested. Both the sequential and parallel auction algorithms perform signi cantly worse than a state-of-the-art Dijkstra-like reference algorithm.
Abstract Over the past decade, cross-docking has emerged as an important material handling technology in transportation. A variation of the well-known Vehicle Routing Problem (VRP), the VRP with Cross-Docking (VRPCD) arises in a number of... more
Abstract Over the past decade, cross-docking has emerged as an important material handling technology in transportation. A variation of the well-known Vehicle Routing Problem (VRP), the VRP with Cross-Docking (VRPCD) arises in a number of logistics planning contexts. This paper addresses the VRPCD, where a set of homogeneous vehicles are used to transport orders from the suppliers to the corresponding customers via a cross-dock.
A zoonotic contribution to the spread of extended-spectrum-lactamase (ESBL)-producing Escherichia coli at the community level has been proposed repeatedly (3), but information on the origin and frequency of ESBLs within different animal... more
A zoonotic contribution to the spread of extended-spectrum-lactamase (ESBL)-producing Escherichia coli at the community level has been proposed repeatedly (3), but information on the origin and frequency of ESBLs within different animal reservoirs is still limited. To improve the current understanding of the evolution and epidemiology of ESBLs in poultry farming, we investigated the occurrence of ESBL-producing E.
Abstract The world's second largest producer of pork, Danish Crown, also provides a fresh meat supply logistics system within Denmark. This is used by the majority of supermarkets in Denmark. This article addresses an integrated vehicle... more
Abstract The world's second largest producer of pork, Danish Crown, also provides a fresh meat supply logistics system within Denmark. This is used by the majority of supermarkets in Denmark. This article addresses an integrated vehicle routing and driver scheduling problem arising at Danish Crown in their fresh meat supply logistics system. The problem consists of a 1-week planning horizon, heterogeneous vehicles, and drivers with predefined work regulations.
This paper contains a cost-benefit analysis of the existing temperature and salinity observing system for the North Sea/Baltic Sea region. The aim of the analysis is to provide a basis for decision makers to make an informed decision on... more
This paper contains a cost-benefit analysis of the existing temperature and salinity observing system for the North Sea/Baltic Sea region. The aim of the analysis is to provide a basis for decision makers to make an informed decision on how to design the future observing system.
Discussion Here we describe the first isolation of LA-MRSA CC398 from dairy cattle in the UK. This is only the second published instance of LA-MRSA CC398 in this country following the report of isolates (t011 and SCCmec IVa) from two... more
Discussion Here we describe the first isolation of LA-MRSA CC398 from dairy cattle in the UK. This is only the second published instance of LA-MRSA CC398 in this country following the report of isolates (t011 and SCCmec IVa) from two horses in south-eastern England [11]. In many countries in continental Europe and elsewhere, LA-MRSA CC398 poses an occupational risk for those in close contact with livestock, particularly pigs and veal calves.
The Vehicle Routing Problem with Time Windows iS a generalization of the well known capacity constrained Vehicle Routing Problem. A homogeneous fleet of vehicles has to service a set of customers. The service of the customers can only... more
The Vehicle Routing Problem with Time Windows iS a generalization of the well known capacity constrained Vehicle Routing Problem. A homogeneous fleet of vehicles has to service a set of customers. The service of the customers can only start within a well—defined time interval denoted the time window. The objective iS tO determine routes for the vehicles that minimizes the accumulated cost (or distance). Currently the best approaches for determining optimal solutions are based on column generation and Branch. and.
In the Home Care Crew Scheduling Problem a staff of home carers has to be assigned a number of visits to patients' homes, such that the overall service level is maximised. The problem is a generalisation of the vehicle routing problem... more
In the Home Care Crew Scheduling Problem a staff of home carers has to be assigned a number of visits to patients' homes, such that the overall service level is maximised. The problem is a generalisation of the vehicle routing problem with time windows. Required travel time between visits and time windows of the visits must be respected. The challenge when assigning visits to home carers lies in the existence of soft preference constraints and in temporal dependencies between the start times of visits.
Abstract The objective of this survey is to cover the research in the area of adaptive traffic control with emphasis on the applied optimization methods. The problem of optimizing traffic signals can be viewed in various ways, depending... more
Abstract The objective of this survey is to cover the research in the area of adaptive traffic control with emphasis on the applied optimization methods. The problem of optimizing traffic signals can be viewed in various ways, depending on political, economic and ecological goals. The survey highlights some important conflicts, which support the notion that traffic signal optimization is a multi-objective problem, and relates this to the most common measures of effectiveness.
Abstract Efficiently coordinating the often large number of interdependent, timetabled train movements on a railway junction, while satisfying a number of operational requirements, is one of the most important problems faced by a railway... more
Abstract Efficiently coordinating the often large number of interdependent, timetabled train movements on a railway junction, while satisfying a number of operational requirements, is one of the most important problems faced by a railway company. The most critical variant of the problem arises on a daily basis at major railway junctions where disruptions to rail traffic make the planned schedule/routing infeasible and rolling stock planners are forced to re-schedule/re-route trains in order to recover feasibility.