Just-In-Time Delivery of Wheel Sets

NedTrain, a subsidiary of the Dutch Railways (NS), is responsible for maintenance of rolling stock of NS. Maintenance is performed at maintenance depots and involves wheel sets that are located under trains. Wheels are subject to wear due to usage and need to be exchanged at maintenance when they have worn below a certain limit. Therefore, it is key to have a certain set (types and amount) of wheel sets available for upcoming maintenance to prevent non-availability of trains. At this moment wheel sets are stocked at different locations. However, NedTrain intents to concentrate wheel set stock at a central depot, and to supply wheel sets Just-In-Time to local maintenance depots. It is believed that in this way the turnaround stock of overhauled wheel sets can be reduced. Insight in the interaction between departments is provided with an overview of the wheel set chain. At this moment two forecasting methods for wheel set demand are used. Maintenance depots plan demand one week ahead by using information from NS Reizigers on planned train arrivals. The overhaul depot forecasts supply four weeks ahead, based on former overhaul levels. It is observed that little information on future demand is exchanged and demand beyond four weeks is unknown. Wheel wear has shown a more deterministic behavior since a use-based maintenance policy for wheel sets has been introduced for intercity rolling stock of NS as of 2007. Since demand patterns have not been changed and current forecasts based on former overhaul/demand levels shows varying results an alternative forecasting approach has been developed. This forecast approach is based on actual wheel set conditions and wheel wear. Wheel wear at wheel lathes is 2 - 6 times as high than wear during operation. A selection of wheel wear causes is made, based on short-term influences, which are used as variables in the forecast method. An overview of causes is included in Appendix I. In this report six different methods of forecasting wheel set demand are studied and validated with 2012 demand. Wheel set demand is forecasted based on wheel set exchanges due to passing a wear limit, which covered 86% of wheel set exchanges in 2012. The best performing method is selected on the lowest error between forecasted versus real demand in the first three months. Validation shows that wheel set demand can be forecasted with a Mean Absolute Deviation of 26 - 27 days, which exceeds the current planning horizon of maintenance depots. The best performing method includes fuzzy logic to account for temporary increased wear rates due to maintenance, stage of wear and seasonality. Forecasted failure dates of wheel sets are rounded down to future maintenance periods. The current accuracy on short-term is considered as too low to serve as reliable basis for determining a required level of wheel sets to supply maintenance depots with an interval of one month and wheel set availability of 90%. The application of fuzzy logic and tuning has improved accuracy on monthly levels, but still demand for wheel sets is frequently overestimated. For this reason Just-In-Time delivery of wheel sets, based on current demand patterns and forecast accuracy, is currently not the designated solution to supply maintenance depots at NedTrain. In this report is shown that diameters within a population of wheel sets are not always equally distributed, which results in troughs and peaks in demand. The forecast accuracy on mid-term is accurate enough to provide insight for NedTrain in these future demand patterns for at least 2 years ahead. This information might be used as guideline for mid or long-term decisions on future overhaul and stock levels of wheel sets. Improvements are proposed for the forecast model and with regard to NedTrain practices to help increase predictability of future wheel set demand.Mechanical, Maritime and Materials EngineeringMarine and Transport TechnologyTransport Engineering and Logistics2013.TEL.779

Bètadidactiek: Kunstje, kunst of kunde: naar een R&D cultuur voor de bètadidactiek

Applied Science

Flooding: Classification and simulation

Flooding of an area can be described mathematically and by the use of scale models. The different flow regimes can be discerned using the scale model and then these regimes can be modelled using mathematical relations. This mathematical description can then be used to design simulation computer code for such a flooding. The first part ofthis report describes the different flow regimes that can occur after a defence work fails. For all regimes estimations were done of the dependence ofthat regime on measured data and of calculation methods. This report shows that the dynamic terms in the mathematical hydraulic descriptions have the upper hand during the first parts of the flooding. Later friction terms become more important. The dynamic terms prove to be highly dependent on the correct implementation of the mathematical relation in the simulation computer code. Bottom friction depends more on correct data from the field. The second part of the report describes the verification of the capabilities of DELFT-FLS to simulate dynamic flow accurately. An improvement on the correct handling of straight closed bevelled boundaries was implemented. With the simulation of and comparison to a dam-break laboratory experiment the correct implementation of mathematical descriptions of flow is shown.Hydraulic EngineeringCivil Engineering and Geoscience

Wicked problems in a technological world

In this article, the morality in the “wickedness” of design problems as wicked problems is explored. I will use for that purpose the characteristics of wicked problems as identified by Horst Rittel and Melvin Webber. These characteristics suggest interdisciplinary thinking for solving such problems. An awareness of the wicked nature of design problems can stimulate proper use of the concept of utopias for solving these problems. I will use the philosophy of Herman Dooyeweerd to provide a framework for understanding the nature of design problems as wicked problems.Science Education and CommunicationEthics & Philosophy of Technolog

What preconceptions and attitudes about engineering are prevalent amongst upper secondary school pupils? An international study

n the Netherlands, as well as in many other countries, there is an increasing interest in implementing education about engineering as a part of general education at the upper secondary school level. In order to know what pupils at that level think about engineering, a study has been done to investigate their attitude towards and their concept of engineering. This study was done not only in the Netherlands but also in 39 other countries. In the preparation of the study, pupils were asked to draw concept maps of what they thought engineering was about. In the quantitative main part of the study, pupils were asked to respond to 33 Likert-type attitude items and 32 concept-items of the same type. A factor analysis was done in order to reveal the dimensions in the pupils’ attitude and concept. In contrast to studies carried out amongst students in lower secondary school levels, a fairly clear concept about engineering was found. The gender differences relating to engineering, found in lower secondary education, were not found in upper secondary education. The prevalent attitude of students towards engineering indicated a fairly positive image of engineering.Applied Science

The Future of Technology Education in the ‘Low Lands’: Experts’ Views in Flanders and the Netherlands

In 2020 an article about USA experts’ opinions on the future of technology education was published. Several concerns were expressed by the experts in the Delphi study that had been conducted, such as a shortage of teachers and funding. From the start of the study in USA the idea was to conduct similar studies in other countries. In Finland such a study has also been done but the outcomes have not been published yet. It is interesting to see to what extent the outcomes are USA specific or more broadly valid. To find that out a similar study was done also in Flanders (the Dutch-speaking part of Belgium) and the Netherlands. It became clear that there are similarities between the USA outcomes but also differences. Most of those differences can be explained by taking into account the local developments in the different countriesScience Education and Communicatio

Models as artefacts of a dual nature: A philosophical contribution to teaching about models designed and used in engineering practice

Although ‘models’ play a significant role in engineering activities, not much has yet been developed to enhance the technological literacy of students in this regard. This contribution intends to help fill this gap and deliver a comprehensive account as to the nature and various properties of these engineering tools. It begins by inspecting two well-known cases: the long-term policy documents of technological literacy in the USA and in New Zealand. This will help to clarify the approach of these educational documents to models, provide a primary understanding of their existing drawbacks in this relation, and realize the necessity of underpinning a well-organized account that can be used in teaching about models. Next, the discussion moves toward an attempt to develop a sound description of the nature of models. This is accomplished through an extensive review of the viewpoints of philosophers (of science and technology) about the nature and properties of these tools; models will then be argued and suggested for consideration as techno-scientific artefacts with their own dual nature: the intrinsic and the intentional. Such an account paves the way to the next step, which namely attempts to provide a well-ordered framework of the models’ various properties, through taking up those two natures and their interrelation in detail. The paper concludes by showing some initial advantages of applying the suggested approach to the intended cases, which can hopefully lead to further, more detailed inspections and extended contributions.Applied Science

'Standards' on the bench: Do standards for technological literacy render an adequate image of technology?

The technological literacy of students has recently become one of the primary goals of education in countries such as the USA, England, New Zealand, Australia, and so forth. However the question here is whether these educations - their long-term policy documents as well as the standards they provide in particular - address sufficient learning about the nature of technology. This seems to be an important concern that through taking advantage of the philosophy of technology (the arena which affords a bountiful ground of various reflections on the nature of technology) is intended to be discussed throughout this study. In the first place, the paper presents a relevant framework based upon Mitcham's (1994) four-aspect account of technology, i.e., technology as objects, knowledge, activities, and volition. Then it categorizes the main relevant concepts and concerns put forward by many other philosophers of technology into this framework; this will yield a concrete model (tool) to analyze any intended standard such as the above mentioned ones. Afterwards, to show how this model works, the well-known case of the USA - Standards for Technological Literacy (ITEA, 2007) - will be used as an example for inspection; the results will disclose the points where the current American case needs to be modified.Science Education and Communicatio

An Appraisal of Qualifying Role of Hydraulic Heritage Systems: A Case Study of Qanat in the Central Iran

Hydraulic heritage systems, both underground and exposed, have been known to be sustainable for millennia. Persian and also Roman aqueducts are examples of such hydrosystems. Their value is often overlooked but they have undeniable advantages: they have functional interconnectedness with their surrounding society and ecology, which sometimes leads to revitalization plans. By using the notion ‘qualifying role’, this paper will raise questions concerning the disregarded functions and early and historical positions of hydraulic heritage systems. This article illustrates the qualifying role of Qanats in urban drainage by describing the skill in their planning and construction. This is shown by a problematic case study in Iran, where the construction of a drainage system modelled on bygone Qanat techniques resulted in a dramatic drawdown in the water level of the area soon after construction.Hydraulic EngineeringCivil Engineering and Geoscience