On non-permutation solutions to some two machine flow shop scheduling problems

In this paper, we study two versions of the two machine flow shop scheduling problem, where schedule length is to be minimized. First, we consider the two machine flow shop with setup, processing, and removal times separated. It is shown that an optimal solution need not be a permutation schedule, and that the problem is NP-hard in the strong sense, which contradicts some known results. The tight worst-case bound for an optimal permutation solution in proportion to a global optimal solution is shown to be 3/2. An O(n) approximation algorithm with this bound is presented. Secondly, we consider the two machine flow shop with finite storage capacity. Again, it is shown that there may not exist an optimal solution that is a permutation schedule, and that the problem is NP-hard in the strong sense

Routing trains through railway stations: complexity issues

In this paper we consider the problem of routing trains through railway stations. This problem occurs as a subproblem in the project DONS that is currently being carried out under the supervision of Railned and Netherlands Railways. The project DONS involves the determination of the required future capacity of the Dutch railway infrastructure. In this paper we focus on the computational complexity of the problem of routing trains through railway stations. After an extensive description of the problem, we show that only a subset of the sections and routes of a railway station needs to be taken into account. Then we show that the routing problem is NP-complete as soon as each train has three routing possibilities. However, if each train has only two routing possibilities, then the problem can be solved in an amount of time that is polynomial in the number of trains. Furthermore, if the layout of the railway station is fixed, then the latter is also the case for the problem of finding an assignment of a maximum number of trains to routes that is feasible from a safety point of view. This result can be extended to the case where coupling and uncoupling of trains, certain service considerations, and a cyclic timetable have to be taken into account

Firm Heterogeneity and Exports in The Netherlands: Identifying Export Potential

Stimulating firms to become exporters is of interest to policy makers, as exporters are in general more productive than non-exporters. However, selecting high export potentials is difficult in practice. The contribution of this paper is to characterize and identify these (high) export potentials. According to the Melitz (2003) model, potential exporters have to be productive enough to overcome the entry costs of foreign markets. Once firms pass this productivity threshold, they all export. Empirical evidence, however, indicates that a substantial share of high-productive firms does not export. In this paper, we focus specifically on this group of high-productive non-exporters. We employ a large micro-dataset for Dutch firms both in services and manufacturing for 2010-2014. Our findings are threefold. First, high productivity is an important, but not a sufficient condition for exporting. Firm size (substitute for productivity), import status, and foreign ownership are also important. Second, firm location is crucial. A location in peripheral areas prevents high productive firms from exporting; especially a location in the Northern part of the Netherlands reduces the probability to export. Third, the manufacturing sector differs from the services sector. Given that the median exporter in our sample is a services firm; this sector should be included in export research

Cost-benefit analysis for flood risk management and water governance in the Netherlands; an overview of one century

The Netherlands is a global reference for flood risk management. This reputation is based on a mix of world-class civil engineering projects and innovative concepts of water governance. For more than a century, cost-benefit analysis has been important for flood risk management and water governance in the Netherlands. It has helped to select the most effective and efficient flood risk projects and to coordinate and reconcile the interests of various policy areas, levels of government and private stakeholders. This paper provides for the first time an overview of this well-developed practice. This includes the cost-benefit analysis in the 1901 act for enclosure of the Zuiderzee, van Dantzig’s famous formula for the economically optimal strength of dikes and a whole set of cost-benefit analyses for More room for rivers and the Delta Program for the next century. Dutch practice illustrates how cost-benefit analysis can support and improve flood risk management and water governance; other countries may learn from this. Rough calculations indicate that investing in cost-benefit analysis has been a highly profitable investment for Dutch society

Reële opties en de waarde van flexibiliteit bij natte infrastructuur

The basic idea of real options analysis is that flexibility has value. Increasing the flexibility of investmentprojects may therefore substantially increase their value. Ignoring the value of flexibility implies that erroneously investmentprojects without much flexibility may be preferred to more flexible alternatives. This paper investigates how real options analysis can be applied to the Dutch practice of water infrastructure, like the replacement and maintenance of current water construction works (e.g. bridges, dams and sluices) and the new Deltaprogram investments. The major conclusion is that identifying the various options for flexibility is usually more important than the estimation of their value. Estimation of the value is not necessary if sensitivity analysis indicates that a specific option for flexibility is a no regret solution that is in all circumstances preferrable to the other options. In case valuation is required to identify the best option, the best strategy is to start with simple and rough estimates using different sets of assumptions. Further refinement and improvement of these estimates could be counterproductive: considering the great uncertainty about future developments and the volatility of the value of options this will often not lead to much more accurate estimates. Furthermore, the increased complexity of the analysis will in practice often lead to substantial drawbacks in terms of communication and decision-making

Een snelle kosten-effectiviteitsanalyse voor het Deltaprogramma IJsselmeergebied: wat zijn de kosten en veiligheidsbaten van wel of niet meestijgen met de zeespiegel en extra zoetwaterbuffer?

Changes in the climate will have a major impact on the Dutch economy and environment. According to official Dutch climate scenario’s, at the end of the century the sea level will have increased by between 35 and 85 cm. This paper investigates major policy options for the IJsselmeer-area to ensure safety against flooding and various options to increase the freshwater stock. It is concluded that the costs to ensure safety and to protect the citizens, economy and the environment are substantial, that installing massive pumps results in major savings and that in the short run the fresh water stock can be tripled at very low costs (25 million euro). In contrast to the suggestion by the second Dutch Delta Commission, the water level in the IJsselmeer need not rise in line with the sea level The costs of raising dikes and safety benefits were calculated using the model Diqe-Opt. In addition, also all kinds of secondary costs and benefits were investigated, like the effects of changing the water level for the environment, shipping, agriculture and historic monuments built on long wooden piles. The effects on the environment were incorporated in several different ways. One approach was to estimate the costs to prevent environmental damage. For biodiversity, the shallow parts of the IJsselmeer are the most important. These can be protected against a rising water level by constructing a sand barrier. An alternative option is to purchase agricultural land and to use this for environmental purposes. In addition to these cost estimates, also the effects on biodiversity without any additional policy measures were investigated. This was measured in two different ways: the extent to which legal environmental protection standards were met and the score in biodiversity points. According to this cost-effectiveness analysis le 5.5), the option to install giant pumps at the Afsluitdijk is billions of euro cheaper than letting the water level rise with the sea level. This holds also when the differences in fresh water buffer are taken into account. Another conclusion of this analysis was that with limited investments (about 25 million euro), the fresh water buffer in the IJsselmeer-region could be tripled in about a decade

Een snelle kosten-effectiviteitsanalyse voor het Deltaprogramma IJsselmeergebied: wat zijn de kosten en veiligheidsbaten van wel of niet meestijgen met de zeespiegel en extra zoetwaterbuffer?

Changes in the climate will have a major impact on the Dutch economy and environment. According to official Dutch climate scenario’s, at the end of the century the sea level will have increased by between 35 and 85 cm. This paper investigates major policy options for the IJsselmeer-area to ensure safety against flooding and various options to increase the freshwater stock. It is concluded that the costs to ensure safety and to protect the citizens, economy and the environment are substantial, that installing massive pumps results in major savings and that in the short run the fresh water stock can be tripled at very low costs (25 million euro). In contrast to the suggestion by the second Dutch Delta Commission, the water level in the IJsselmeer need not rise in line with the sea level The costs of raising dikes and safety benefits were calculated using the model Diqe-Opt. In addition, also all kinds of secondary costs and benefits were investigated, like the effects of changing the water level for the environment, shipping, agriculture and historic monuments built on long wooden piles. The effects on the environment were incorporated in several different ways. One approach was to estimate the costs to prevent environmental damage. For biodiversity, the shallow parts of the IJsselmeer are the most important. These can be protected against a rising water level by constructing a sand barrier. An alternative option is to purchase agricultural land and to use this for environmental purposes. In addition to these cost estimates, also the effects on biodiversity without any additional policy measures were investigated. This was measured in two different ways: the extent to which legal environmental protection standards were met and the score in biodiversity points. According to this cost-effectiveness analysis le 5.5), the option to install giant pumps at the Afsluitdijk is billions of euro cheaper than letting the water level rise with the sea level. This holds also when the differences in fresh water buffer are taken into account. Another conclusion of this analysis was that with limited investments (about 25 million euro), the fresh water buffer in the IJsselmeer-region could be tripled in about a decade

Routing trains through a railway station based on a Node Packing model

In this paper we describe the problem of routing trains through a railway station. This routing problem is a subproblem of the automatic generation of timetables for the Dutch railway system. The problem of routing trains through a railway station is the problem of assigning each of the involved trains to a route through the railway station, given the detailed layout of the railway network within the station and given the arrival and departure times of the trains. When solving this routing problem, several aspects such as capacity, safety, and customer service have to be taken into account. In this paper we describe this routing problem in terms of a Weighted Node Packing Problem. Furthermore, we describe an algorithm for solving this routing problem to optimality. The algorithm is based on preprocessing, valid inequalities, and a branch-and-cut approach. The preprocessing techniques aim at identifying super uous nodes which can be removed from the problem instance. The characteristics of the preprocessing techniques with respect to propagation are investigated. We also present the results of a computational study in which the model, the preprocessing techniques and the algorithm are tested based on data related to the railway stations Arnhem, Hoorn and Utrecht in the Netherlands.mathematical economics and econometrics ;