Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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Sustainable logistics management : from castle on the cloud to cathedral
Bloemhof-Ruwaard, J.M. - \ 2015
Wageningen : Wageningen University, Wageningen UR - ISBN 9789462571969 - 24
logistiek - duurzaamheid (sustainability) - ketenmanagement - operationeel onderzoek - logistics - sustainability - supply chain management - operations research
Critical success factors for implementing supply chain information systems : insights from the pork industry
Denolf, J.M. - \ 2014
University. Promotor(en): Onno Omta; Jack van der Vorst, co-promotor(en): Jacques Trienekens. - Wageningen : Wageningen University - ISBN 9789462571594 - 177
operationeel onderzoek - ketenmanagement - informatiesystemen - varkens - vee- en vleesindustrie - operations research - supply chain management - information systems - pigs - meat and livestock industry

Critical success factors for implementing supply chain information systems – Janne M. Denolf

Due to intensified competition, companies realize that they should closely collaborate with their supply-chain partners to further cut costs and stay competitive. To do so, supply-chain partners should intensify information sharing, which is often facilitated through supply chain information systems (SCIS). Implementation of such a system is a complex undertaking due to the umpteen technical and organizational aspects that require consideration. Multiple theories have given valuable insights into the complex interplay of organization and technology. However, tangible tools that consider these theories for implementing a supply chain information system are scarce. To provide more ready-to-use methods, the main objective of the thesis is to identify organizational and technical critical success factors (CSFs) for sharing information and implementing supply chain information systems (SCISs). CSFs are the factors that must go well during an implementation and must, therefore, be given special and continual attention in order to successfully implement an information system. This central objective is investigated by means of the pork industry.

In Chapter 2, we pay particular attention to (supply chain) information sharing. The literature indicates that the relationships among the supply-chain partners have to be managed, and effective governance structures need to be chosen for effective and efficient information sharing. Despite initial research, the literature has not accounted for the multi-dimensionality of information sharing and does not consider the complete supply chain as the unit of analysis. This leads to the first research objective: to investigate how and to what extent supply chain information sharing can be explained by supply chain governance structures. To gain insights regarding the research objective, three European pork supply chains with different governance structures were investigated. Through cross-case analysis, the study stipulates that apart from governance structures, quality regulations, the financial strength (of one or more supply-chain partners) and relationship management seem to influence information sharing to a great extent.

As stated in Chapter 2, supply chains increasingly share information through implementing automated SCISs. To manage these implementations carefully, the study of CSFs for SCIS implementations forms a promising approach. Since to date no consensus has been reached on SCIS critical success factors, the second objective is to identify critical success factors for implementing SCISs. Based on 10 key articles focusing on ERP implementations, we have built a list of CSFs as a starting point for the SCIS literature search. Thereafter, based on 21 SCIS articles, 14 CSFs for supply-chain information system implementation have been defined. To indicate the nature of the CSFs and highlight the interaction of the organizational and technical system, the CSFs are classified in the MIT90s framework of Scott Morton (1991) (See Figure 1).

Figure 1. Framework of CSFs for SCIS implementations

Chapter 3 identifies a comprehensive framework of CSFs for implementing SCISs. Concrete guidance for applying CSFs has, however, not been provided by the CSF literature. There is a gap between the rather abstract CSFs for SCIS implementations and operational project management. Consequently, the following third objective is posed: to make critical success factors for implementing supply chain information systems “actionable”. To deal with this objective, we investigated the completed implementation of SCISs in four German pork supply chains. Respondents were asked to describe crucial challenges during the project and actions taken to cope with these challenges (i.e. Critical Incident Technique). Challenges were assigned to CSFs and form a basis upon which to take actions. Our results suggest that “convince future users to use the new SCIS” – part of the CSF “manage change and deliver training” – and “define the functional requirements of the SCIS” – part of the CSF “select standards, vendor, and software package” – are frequently mentioned challenges. Furthermore, possible critical actions – with connected supply-chain responsibilities – are identified for implementing a SCIS. All in all, through this research, we link the concepts CSFs, challenges, and actions and bridge the gap between CSFs and operational project management for the implementation of a SCIS.

The fourth research objective deals with traceability systems, which are specific SCISs, aiming at the collection, documentation, maintenance, and application of information related to all processes in the supply chain in a manner that provides guarantees to consumers and stakeholders on origin, location, and life-history of a product. Despite a number of traceability and RFID publications, these publications fall short as they often deal with the general issue of traceability and are not really applicable for practitioners. Identification of critical traceability points (CTPs), which are points where information regarding traceability may get lost, is a suitable method for making traceability research more applicable. At last, the following fourth research objective is posed: to identify CTPs in organic pork supply chains and to investigate how these CTPs can be managed through the application of RFID in these chains. Data were collected through an in-depth case study in the European organic pork industry. After having mapped the production processes and information flows for farm and slaughterhouse, CTPs were identified. To keep such information available for actors in the supply chain, pigs should be uniquely identified throughout the supply chain and transformations at farm and slaughterhouse recorded. In the supply chain investigated, 18 CTPs are identified. Then, it was verified how and to what extent CTPs could be managed using RFID applications. The results indicate that several CTPs can be managed using RFID, but additional organizational measures, and the use of other identification technologies, such as DNA profiling, are imperative to manage all CTPs. On top of that, a new SCIS should be built, coupling different existing computer systems of actors involved.

On a general level, this thesis makes a contribution to the theories examining and explaining the mutual interaction of organizational and technical aspects. Specifically, tangible tools are provided that consider these theories for implementing SCISs. Organizational and technical critical success factors – and connected actions – are identified and classified in the MIT90s framework, which is in line with the Structuration Theory of Orlikowski (1992) and reflects the project life cycle of Markus and Tanis (2000). Using the framework of 14 CSFs, a more ready-to-use method is provided for implementing SCIS. Specifically, the thesis makes contributions to the literature on critical success factors (CSF) and critical traceability points (CTP). First, by identifying critical success factors (CSFs) for implementing SCISs, the CSF literature base is extended. Moreover, through identification of key actions for the CSFs, this thesis responds to a stream of researchers claiming that CSFs are not “actionable”. Second, compared to previous research, we investigate how and to what extent critical traceability points can be managed using new technologies such as Radio Frequency Identification (RFID). By verifying best practices and applications for RFID deployment, we provide a response to a group of researchers who stated that RFID and traceability research are not really applicable for practitioners.

Optimization-based decision support systems for planning problems in processing industries
Claassen, G.D.H. - \ 2014
University. Promotor(en): Jack van der Vorst. - Wageningen : Wageningen University - ISBN 9789462572089 - 171
operationeel onderzoek - logistiek - voedselverwerking - voedselindustrie - pulp- en papierwarenindustrie - beslissingsondersteunende systemen - optimalisatie - procesoptimalisatie - wiskundige modellen - operations research - logistics - food processing - food industry - pulp and paper industry - decision support systems - optimization - process optimization - mathematical models

Summary

Optimization-based decision support systems for planning problems in processing industries

Nowadays, efficient planning of material flows within and between supply chains is of vital importance and has become one of the most challenging problems for decision support in practice. The tremendous progress in hard- and software of the past decades was an important gateway for developing computerized systems that are able to support decision making on different levels within enterprises. The history of such systems started in 1971 when the concept of Decision Support Systems (DSS) emerged. Over the years, the field of DSS has evolved into a broad variety of directions. The described research in this thesis limits to the category of model-driven or optimization-based DSS.

Simultaneously with the emergence of DSS, software vendors recognized the high potentials of available data and developed Enterprise Systems to standardize planning problems. Meanwhile, information oriented systems like MRP and its successors are extended by the basic concepts of optimization based decision support. These systems are called Advanced Planning Systems (APS). The main focus of APS is to support decision making at different stages or phases in the material flow, i.e. from procurement, production, distribution to sales (horizontal-axis), on different hierarchical aggregation levels (vertical-axis) ranging from strategic (long-term) to operational (short- term) planning. This framework of building blocks decomposes planning tasks hierarchically into partial planning problems. This basic architecture of the planning processes in APS is known as the Supply Chain Planning Matrix (SCPM).

Compared to, for instance, discrete parts manufacturing, planning tasks are much more complicated in processing industries due to a natural variation in the composition of raw materials, the impact of processing operations on properties of material flows, sequence dependent change-over times, the inevitable decline in quality of product flows and relatively low margins. These specific characteristics gave rise to focus on optimization-based decision support in the domain of processing industries. The problems to be addressed in this field call for (inter-related) decisions with respect to the required raw materials, the production quantities to be manufactured, the efficient use of available resources, and the times at which raw materials must be available.

Although different APS modules can interact directly, coordination and integration is often restricted to the exchange of data flows between different modules. Given the need for specific integrated decision support, the research presented in this thesis focusses particularly on medium to short term decision support at production stage in processing industry, including the vertical and horizontal integration and coordination with adjacent building blocks in the SCPM.

Extensive reviews from literature show that the gap between research and practice of DSS is widening. As the field of DSS was initiated as an application oriented discipline, the strategy of what is referred to as “application-driven theory” was taken as the preferred approach for this thesis. “Application-driven” refers to a bottom-up approach which means that the relevance of the research should both be initiated and obtained from practice. The intended successful use of the proposed approaches should, where possible, be represented by tests of adequacy. Simultaneously, the contribution to “theory” aims to be a recognizable part of the research effort, i.e.

obtained understanding and insights from problems in practice should provide the basis for new approaches. Based on the preceding considerations we defined the following general research objective:

General research objective

To support medium- to short term planning problems by optimization-based models and solution techniques such that:

i) The applicability and added value of (prototype) systems is recognized and carried by decision makers in practice

ii) The proposed approaches contribute to knowledge, understanding and insights from a model building and solving point of view.

In order to link the general objective with the different studies in the thesis, we defined five, recurring research premises, i.e. Professional relevance and applicability (P1), Aggregation (P2), Decomposition and reformulation (P3), Vertical integration at production level (P4), and Horizontal coordination and integration (P5).

The overarching premise P1 refers to the first part of the research objective. All other premises refer to the second part of the research objective, i.e. model building and/or – solving. Several planning issues are studied to give substance to the research objective and each study is connected to at least two research premises.

Study 1: Planning and scheduling in food processing industry

The main question in Chapter 2 was:” How to apply aggregation, decomposition and reformulation in model-based DSS at planning and scheduling level such that the aspect of decision support is recognized and appreciated by decision makers in practice, and which level of aggregation is needed to integrate production planning (i.e. lot-sizing) and scheduling problems in a single model?

The study consists of two parts. The first part of the study refers to a case study for the bottleneck packaging facilities of a large dairy company. The goal was to develop, implement and test a pilot DSS which was able to deliver solutions recognized and carried by decision makers at lower decision levels. The latter aim implied that a straight-forward aggregation on time, product type, resources or product stage, was not preferred. The key to develop an approach for regular use was to identify and take advantage of specific problem characteristics. Clustering of numerous jobs, while retaining information at order level, could be exploited in a reformulation approach. The inclusion of (combined) generalized- and variable upper bound constraints gave very tight lower bounds and sparse search trees.

An extensive test phase in daily practice showed that the main benefit of the DSS was the initial quality of the generated plans including the time needed to generate these schedules. Hence, decision makers could i) postpone their planning tasks, ii) conveniently cope with rush orders or planned maintenance and iii) easily generate

alternatives or revised plans when unforeseen disturbances occur. Moreover, the graphical presentation and overview of the (future) working schedule enabled order acceptance to make use of remaining capacity.

The study also showed that planning problems in practice cannot be captured exhaustively by a (simplified) model. Decision makers need the opportunity to modify automatically generated plans manually and use human judgement and experience such that the solution is tuned to the actual situation. Hence, the DSS should not be considered as an optimizer but rather as a tool for generating high quality plans to be used for further analysis. Within this context the various options of a user-friendly, graphical, and fully interactive user interface, were of major importance.

Although the case study clearly demonstrates the validity of earlier case based DSS research for current days APS, the proposed approach is hardly a generic solution for a complete vertical integration between lot-sizing and scheduling. If lot-size decisions are strongly affected by the sequence of jobs, production planning and scheduling should be performed simultaneously.

As the described case refers to an earlier study and today’s APS do not provide modules for integrated lot-sizing and scheduling, the second part of the study gives an overview of developments in literature regarding lot-sizing and scheduling models and assess their suitability for addressing sequence-dependent setups, non-triangular setups and product decay. The review shows a tendency in which so-called Big Bucket (BB) models are currently proposed for short term time horizons too. However, we argue that segmentation of the planning horizon is a key issue for simultaneous lot-sizing and scheduling. The advantage of BB models may become a major obstacle for i) the effectiveness of simultaneous lot-sizing and scheduling, and ii) addressing specific characteristics in food processing industry.

Study 2: Vertical integration of lot-sizing and scheduling in food processing industry

Chapter 3 focused on a complete integration of lot-sizing and scheduling decisions in a single model. The main question was:” How to integrate production planning (i.e. lot- sizing) and scheduling problems in a single model, such that common assumptions regarding the triangular setup conditions are relaxed and issues of product decay and limited shelf lives are taken into account?”

The literature research in Chapter 2 revealed that the computational advantage of time oriented aggregation in BB models may become a major obstacle in addressing the identified characteristics in FPI. In addition, product decay is primarily associated with the “age” of products and consequently relates to the segmentation of the time- horizon. Therefore, two SB models are developed to demonstrate the impact of non- triangular setups and product decay on the generated solutions. Small scale examples were used to demonstrate how a small change in the balance between inventory - and

changeover costs may generate significantly different solutions, especially when the triangular setup conditions do not hold.

The developed models are potentially very large formulations and, as expected, hard to solve. Exploratory research was conducted with a Relax-and-Fix (R&F) heuristic. The heuristic is based on a decomposition of the time horizon. Numerical results of small to medium sized problem instances are promising. However, solving real-size problem instances is not possible yet.

Study 3: Integrated planning between procurement and production

The case study in Chapter 4 focussed on the need for horizontal coordination and integration between the phases procurement and production, which is of particular importance in inter-organizational supply chains. The main question was:” How to model and solve an integrated planning problem between procurement and production, both on a mid-term and short-term planning level, in an inter-organizational supply chain? The research question was projected on an illustrative milk collection problem in practice.

The aim was to develop a pilot DSS that lifted decision support for a “weaker” partner in a food supply chain to a higher level, and to illustrate the importance of horizontal integration between the phases procurement and production in an APS framework.

Problem analysis revealed that the problem can be classified as an extension of the Periodic Vehicle Routing Problem (PVRP). The problem was decomposed into more tractable sub problems on different hierarchical levels, i.e. the daily (vehicle) routing problem was separated from a medium-term planning problem. On the higher planning level, numerous suppliers were aggregated such that total supply within a cluster met (multiple) vehicle loading capacities. The continuous supply of relatively small amounts from many suppliers had to be balanced with strict delivery conditions at processing level. A model was developed to assign a single (stable) collection rhythm to each cluster such that the total, weighted deviation of desired processing levels on various days in the planning horizon was minimized.

The applied aggregation on the higher planning level turned out to be very beneficial for the required disaggregation at the lower planning level. Once supplier farms were geographically grouped into clusters and the aggregated supply within a cluster was assigned to a single collection rhythm with fixed collection days, the (initial) daily routing problem was considerably easier to solve for vehicle schedulers.

The computational complexity of the problem was reduced by exploiting application-based properties algorithmically in a specific branch-and-bound scheme, i.e. a customized approach of Special Ordered Sets type 1 (SOS1) This approach made it possible to solve the generated problems exactly for real-size problem instances.

The various facilities of a user-friendly and interactive man-machine interface (i.e. an input, planning, simulation and analysing module) turned out to be essential. Decision makers could easily change the data, and the generated plans, in a separate simulation module. However, the impact of any modification was immediately visualised by several (conflicting) indicators in the output screens, both on supply and demand level.

Study 4: Mixed Integer (0-1) Fractional Programming in Paper Production Industry

The study in Chapter 5 focussed on the impact of technical settings of production units on material flows. The main question was:” How to support decision-makers in practice if crucial properties of end products simultaneously depend on (endogenous) types of raw materials with different chemical or physical properties and (endogenous) technical settings of processing units?

The goal of the study was to revise and upgrade an existing, locally used DSS, to a tailored and flexible tool for decision support within the enterprise. The study revealed that the aimed extension towards multi-objective decision support, together with new physical insight for calculating properties of end products due to process operations, had a substantial impact on the optimization module.

The proposed solution procedure takes advantage of the problem characteristics and gives rise i) to apply and extend a classical reformulation approach for continuous linear fractional programming (FP) problems to a more general class of mixed integer (binary) FP problems and ii) to exploit the special structure between the original non- linear mixed integer model and the continuous, linear reformulation by applying the concept of Special Ordered Sets type 1 (SOS1).

Although Chapter 5 focusses in particular on the reformulation and solution approach, the DSS consists of four main building blocks, i.e. the user interface, a scenario manager, a simulation- and optimization routine. The optimization module provides a powerful tool to find feasible solutions and the best (unexpected) recipes for any available set of raw materials. Moreover, it provides an innovative way of decision support for purchasing (new) pulps on the market, for assigning available pulps to different paper grades, and for attuning available stock levels of raw materials to (changing) production targets for different paper grades. The results of the optimization routine are mainly used to obtain alternative recipes for different paper grades. Usually, these recipes are stored as base scenarios and adapted to daily practice in the simulation module.

Main conclusions and future research

Based on the studies in the Chapters 2 and 3 we conclude that no generically applicable models and/or solution approaches exist for simultaneous planning and scheduling in processing industries. More industry-specific solutions are needed incorporating specificities of different production environments into those models. The key to develop solvable approaches for contemporary practice may be i) to use knowledge and experience from practice and take advantage of specific characteristics in different problem domains during model construction, and/or ii) to identify and exploit special problem structures for solving the related models.

We conclude that surprisingly little research has been devoted to issues of coordination and integration between “procurement” and “production”. The studies in the chapters 4 and 5 confirm that sourcing of (raw) materials flows needs more attention in processing industries, particularly in push-oriented, inter-organizational networks. The valorisation of raw materials can be improved even more if the composition of raw materials is considered too in future planning problems at production level.

In the second part of this thesis we focused on extensions for the applicability of Special Ordered Sets type 1 (SOS1), both from an algorithmic (Chapter 4) and modelling (Chapter 5) point of view. We conclude that the concept of SOS1 can extend a classical reformulation approach for continuous fractional programming (FP) problems, to a specific class of mixed integer (0-1) FP problems. Moreover, we conclude that a natural ordering of the variables within the sets is not necessary to make their use worthwhile. A separate (user defined) reference row or weights associated to the variables in the sets might be omitted for an efficient use of SOS1 in commercially available mathematical programming packages. However, this requires further research and extensive computational tests.

Decision support modeling for milk valorization
Banaszewska, A. - \ 2014
University. Promotor(en): Jack van der Vorst, co-promotor(en): Frans Cruijssen. - Wageningen : Wageningen University - ISBN 9789461739261 - 182
operationeel onderzoek - modelleren - melk - beslissingsondersteunende systemen - beslissingsmodellen - rentabiliteit - zuivelindustrie - rauwe melk - melkbewerking - nederland - efficiëntie - operations research - modeling - milk - decision support systems - decision models - profitability - dairy industry - raw milk - milk processing - netherlands - efficiency

The research presented in this thesis concerns decision problems in practice that require structured, precise, scientific studies to provide strong, reliable answers. An opportunity to contribute to both practice and science emerged in 2008 when two large, Dutch dairy companies merged, creating FrieslandCampina (FC), which was the fourth largest dairy company in the world at that time. In 2009, a new Milk Valorization & Allocation (MVA) department was created at the corporate level to optimally utilize raw milk (the main raw material) in all business units. The main goal of this research was the development and application of decision support models to help MVA attain its mission of “getting more out of milk.”

The dairy processing industry is a specific and challenging research field. This is related to the fact that the raw milk is transformed into thousands of end products via highly interrelated production processes. These processes are affected by uncertainties related to supply, processing capacities, and demand. Attaining high profitability requires a central, integral planning process that facilitates the optimal allocation of raw milk to a large range of products. Optimal allocation of raw milk is achieved when it is successfully allocated to the most profitable end products and all important constraints are taken into account. This process is defined as milk valorization. Contribution to the improvement of milk valorization in the dairy industry was the main objective of this thesis. We approached the problem from a Logistics Management perspective. We focused on decisions supporting the optimal flow of raw materials to end products, from farmers to consumer markets. With the use of Operations Research techniques, we developed quantitative models and frameworks to improve the mid-term milk valorization process.

As the first step towards the improvement of milk valorization we developed a mid-term Dairy Valorization Model (DVM). The model creates optimal plans for the allocation of milk, and the production of end products and byproducts. It captures the dynamics of dairy production and incorporates all relevant elements and constraints. The following elements were indicated as important and included in the DVM: recipes based on raw milk composition (dry matter, fat, and protein content); seasonality of raw milk composition and supply; a complete dairy product portfolio; by-product utilization; network of supply regions and production locations; by-product and raw milk transportation; and changes in sale prices. Including all relevant elements assures DVM comprehensiveness. This important aspect achieves truly integral valorization of milk. Furthermore, the developed DVM also fosters understanding of complex, underlying production processes. Moreover, by means of additional analysis we have also shown that the seasonality of raw milk components (dry matter, fat and protein) plays an important role in the valorization process. It considerably affects decisions regarding milk allocation to end products (up to 50% difference in production volumes of clustered end products) and company profit (up to 4% difference in monthly profit).

Given the complexity of the dairy system, the development of a high class valorization model required a gradual approach. The developed DVM focuses on the valorization of milk-based end products (main milk products). The production of those products, however, results in large volumes of byproducts.In the second step of this research we investigated the effect of whey valorization (byproduct of cheese) on the valorization of main milk products, as well as the added value of integral valorization (simultaneous valorization of both main and byproducts). We developed a new Integral Dairy Valorization model (IDVM) to allow for an integral milk valorization. We also developed a three-step evaluation approach to compare results of stepwise valorization (in which whey valorization only follows after main milk products valorization) and integral valorization. The results show that the explicit valorization of whey flows leads to significant economic gains for FC. Profit obtained from post processing of whey byproducts amounts to circa 20% of the total profit. Furthermore, the effect of integrating both valorization processes is currently small (on average 0.0089% increase in monthly profit). There is, however, a potential in the integration of two processes. In case demand for, and sale prices of, whey-based products, sale prices of milk powders or processing capacity for whey increases, the gain from the integration can be considerably larger (up to 1200% stronger effect in comparison to the current situation). We have also shown that currently whey products are not profitable enough to drive the production of milk products that are the source of the whey by-product.

In the next step we focused on the accuracy of solutions obtained with the DVM. Because the DVM is a deterministic model, uncertainties present in input are not incorporated, and as such the stability of valorization plans is affected. Stability of plans is often referred as to the ‘robustness’ of plans: the degree to which the optimal solution might change if realization of certain input parameters turn out to be different than the forecasted values. The robustness is important, because the valorization plans that are initially indicated as optimal can easily become sub-optimal or costly. Therefore, the overall goal of the third study was to develop a framework for robustness evaluation of valorization plans obtained with deterministic models. We developed a five-step framework comprised of the following: (1) definition of Key Performance Indicators (KPIs), (2) selection of relevant input parameters, (3) definition of scenarios, (4) evaluation of robustness, and (5) extraction of conclusions. The output from Step 4 of the framework is multidimensional, and thus to arrive at the final robustness degree, a number of decisions must be made a priori: acceptable KPIs limits (robustness bounds); evaluation time (month or year); evaluation depth (parameter or element); and the grouping approach of KPIs. The results show that depending on the selection of these aspects different conclusions regarding robustness of valorization plans are obtained, (average robustness degree varied from 48% to 92%), and thus the final conclusions regarding the robustness degree of plans is affected. The overall robustness degree of valorization plans (at FC) obtained with the DVM was 90% and was indicated by FC as sufficiently high to attain successful milk valorization. The calculated robustness degrees also identified the parameters with the greatest effect on robustness (composition and supply of milk).

The effectiveness of valorization models is mainly linked to the optimality, feasibility and robustness of obtained plans. However, even if these three aspects are satisfied, the success of the valorization process is still very much dependent on the performance level of actors and units that are involved in the process. Given the fact that processing units (factories) are the most important units in the supply chain of a processing company, because they can easily affect the value of each ton of raw milk used in the production process, the last study investigated the performance of processing units. We developed two Data Envelopment Analysis models for performance measurement and improvement, and applied it to the case study of TNT Express. The models allowed us to identify: inefficient units (30%); parts of efficiency levels (of inefficient units) that result from either management practices (85%) or a favorable external environment (15%); potential reductions in consumed input resources that allow for the same output levels (17% less labor and subcontractors could be used); and role models that can be treated as master units in efficient use of certain inputs and thus should play leading roles in setting benchmarks.

We concluded that in order to successfully valorize raw materials, companies should: develop their own valorization model, possess a comprehensible overview of the complete production system; and have access to necessary input data. Furthermore, there is a potential in integrating main product and by-product valorization processes. The added value, however, depends on the information on market and production capacities of by-products and related to them main products. To ensure that possible future integration of both valorizations processes occurs correctly, companies should investigate future market developments and the possibility of increasing production capacity. Moreover, we have also shown that robustness of solutions obtained with deterministic valorization models can be sufficiently high to obtain reliable plans. This means that it is not always necessary to implement complex modeling techniques (such as stochastic programming). To ensure accurate solutions, companies should also focus on improving forecast accuracies of parameters affecting the robustness. The robustness degree should also be regularly assessed with the developed framework. Finally, managers should also focus on performance levels of processing units. A DEA model should be developed to identify inefficient factories and provide new insights to improve performance.

In order to properly valorize milk or other food resources to its maximum an integral point of view should be chosen. Operations Research techniques should be used because the complexity of many processing industries makes applying practical rules of thumb insufficient and often inadequate. The models and frameworks developed in this thesis provide new perspective on and new insights into the complex problem of milk valorizations. We have shown that analyses of results obtained with the developed methods can answer many managerial questions, and thus support the decision making process within a company. This improves overall raw material valorization, creates more value for companies, and leads to more sustainable dairy chains.

Robust food supply supply chains : an integrated framework for vulnerability assessment and disturbance management
Vlajic, J.V. - \ 2012
University. Promotor(en): Jack van der Vorst, co-promotor(en): Rene Haijema. - S.l. : s.n. - ISBN 9789461733641 - 183
operationeel onderzoek - voedselvoorziening - voedselketens - prestatiekenmerken - indicatoren - operations research - food supply - food chains - performance traits - indicators

The operation of supply chains (SCs) has for many years been focused on efficiency, leanness and responsiveness. This has resulted in reduced slack in operations, compressed cycle times, increased productivity and minimised inventory levels along the SC. Combined with tight tolerance settings for the realisation of logistics and production processes, this has led to SC performances that are frequently not robust. SCs are becoming increasingly vulnerable to disturbances, which can decrease the competitive power of the entire chain in the market. Moreover, in the case of food SCs non-robust performances may ultimately result in empty shelves in grocery stores and supermarkets.
The overall objective of this research is to contribute to Supply Chain Management (SCM) theory by developing a structured approach to assess SC vulnerability, so that robust performances of food SCs can be assured. We also aim to help companies in the food industry to evaluate their current state of vulnerability, and to improve their performance robustness through a better understanding of vulnerability issues. The following research questions (RQs) stem from these objectives:
RQ1: What are the main research challenges related to (food) SC robustness?
RQ2: What are the main elements that have to be considered in the design of robust SCs and what are the relationships between these elements?
RQ3: What is the relationship between the contextual factors of food SCs and the use of disturbance management principles?
RQ4: How to systematically assess the impact of disturbances in (food) SC processes on the robustness of (food) SC performances?
To answer these RQs we used different methodologies, both qualitative and quantitative. For each question, we conducted a literature survey to identify gaps in existing research and define the state of the art of knowledge on the related topics. For the second and third RQ, we conducted both exploration and testing on selected case studies. Finally, to obtain more detailed answers to the fourth question, we used simulation modelling and scenario analysis for vulnerability assessment.
Main findings are summarised as follows.
Based on an extensive literature review, we answered RQ1. The main research challenges were related to the need to define SC robustness more precisely, to identify and classify disturbances and their causes in the context of the specific characteristics of SCs and to make a systematic overview of (re)design strategies that may improve SC robustness. Also, we found that it is useful to be able to discriminate between varying degrees of SC vulnerability and to find a measure that quantifies the extent to which a company or SC shows robust performances when exposed to disturbances.
To address RQ2, we define SC robustness as the degree to which a SC shows an acceptable performance in (each of) its Key Performance Indicators (KPIs) during and after an unexpected event that caused a disturbance in one or more logistics processes. Based on the SCM literature we identified the main elements needed to achieve robust performances and structured them together to form a conceptual framework for the design of robust SCs. We then explained the logic of the framework and elaborate on each of its main elements: the SC scenario, SC disturbances, SC performance, sources of food SC vulnerability, and redesign principles and strategies.
Based on three case studies, we answered RQ3. Our major findings show that the contextual factors have a consistent relationship to Disturbance Management Principles (DMPs). The product and SC environment characteristics are contextual factors that are hard to change and these characteristics initiate the use of specific DMPs as well as constrain the use of potential response actions. The process and the SC network characteristics are contextual factors that are easier to change, and they are affected by the use of the DMPs. We also found a notable relationship between the type of DMP likely to be used and the particular combination of contextual factors present in the observed SC.
To address RQ4, we presented a new method for vulnerability assessments, the VULA method. The VULA method helps to identify how much a company is underperforming on a specific Key Performance Indicator (KPI) in the case of a disturbance, how often this would happen and how long it would last. It ultimately informs the decision maker about whether process redesign is needed and what kind of redesign strategies should be used in order to increase the SC’s robustness. The VULA method is demonstrated in the context of a meat SC using discrete-event simulation. The case findings show that performance robustness can be assessed for any KPI using the VULA method.
To sum-up the project, all findings were incorporated within an integrated framework for designing robust SCs. The integrated framework consists of the following steps: 1) Description of the SC scenario and identification of its specific contextual factors; 2) Identification of disturbances that may affect KPIs; 3) Definition of the relevant KPIs and identification of the main disturbances through assessment of the SC performance robustness (i.e. application of the VULA method); 4) Identification of the sources of vulnerability that may (strongly) affect the robustness of performances and eventually increase the vulnerability of the SC; 5) Identification of appropriate preventive or disturbance impact reductive redesign strategies; 6) Alteration of SC scenario elements as required by the selected redesign strategies and repeat VULA method for KPIs, as defined in Step 3.
Contributions of this research are listed as follows. First, we have identified emerging research areas - SC robustness, and its counterpart, vulnerability. Second, we have developed a definition of SC robustness, operationalized it, and identified and structured the relevant elements for the design of robust SCs in the form of a research framework. With this research framework, we contribute to a better understanding of the concepts of vulnerability and robustness and related issues in food SCs. Third, we identified the relationship between contextual factors of food SCs and specific DMPs used to maintain robust SC performances: characteristics of the product and the SC environment influence the selection and use of DMPs; processes and SC networks are influenced by DMPs. Fourth, we developed specific metrics for vulnerability assessments, which serve as a basis of a VULA method. The VULA method investigates different measures of the variability of both the duration of impacts from disturbances and the fluctuations in their magnitude.
With this project, we also hope to have delivered practical insights into food SC vulnerability. First, the integrated framework for the design of robust SCs can be used to guide food companies in successful disturbance management. Second, empirical findings from case studies lead to the identification of changeable characteristics of SCs that can serve as a basis for assessing where to focus efforts to manage disturbances. Third, the VULA method can help top management to get more reliable information about the “health” of the company.
The two most important research opportunities are: First, there is a need to extend and validate our findings related to the research framework and contextual factors through further case studies related to other types of (food) products and other types of SCs. Second, there is a need to further develop and test the VULA method, e.g.: to use other indicators and statistical measures for disturbance detection and SC improvement; to define the most appropriate KPI to represent the robustness of a complete SC. We hope this thesis invites other researchers to pick up these challenges and help us further improve the robustness of (food) SCs.

Ontwikkeling van een nieuw Droog- en Bewaarsysteem : de ontwerpfase
Wildschut, J. ; Sapounas, A. ; Braam, G. - \ 2011
Lisse : PPO Bloembollen en Bomen - 24
bloembollen - opslag met klimaatbeheersing - kratten - ethyleen - opslagruimte - optimalisatie - operationeel onderzoek - energiebesparing - ontwerp - ornamental bulbs - controlled atmosphere stores - crates - ethylene - storage space - optimization - operations research - energy saving - design
Het voordeel van het huidige bewaarsysteem van bloembollen in kuubskisten voor droogwanden in bewaarcellen ligt vooral op het gebied van logistiek. Nadelen zijn het hoge energieverbruik en het ongelijkmatige bewaarklimaat. Op korte termijn kan de bloembollensector nog veel energie besparen door op onderdelen dit systeem te verbeteren. Op langere termijn kan het systeem echter niet verder geoptimaliseerd worden. Daarom is na gegaan of het mogelijk is om een concept van een nieuw systeem te ontwikkelen. Hiertoe zijn in de 4 bloembollenregio’s brainstormsessies georganiseerd. De deelnemende telers, systeembouwers, voorlichters en onderzoekers hebben hierin nieuwe ideeën over bewaarsystemen naar voren gebracht. Deze ideeën zijn vervolgens geordend en samengevat. Hieruit zijn de twee meest perspectiefvolle concepten gekozen en met CFD-berekeningen zijn verschillende varianten onderling en met het huidige kuubskistensysteem vergeleken op basis van energieverbruik per m3 bollen en van gelijkmatigheid van de bewaarcondities. Als belangrijkste criterium bij dit laatste is de variatie in ethyleenconcentratie tussen de bollen. Op basis hiervan zijn varianten van het nieuwe concept nader doorgerekend met als uitgangspunt het zg. “worst case scenario”: 5 % zure bollen.
Development and selection of operational management strategies to achieve policy objectives
Piet, G.J. ; Rockmann, C. ; Aanesen, M. ; Armstrong, C. ; Quesne, W. Le; Bloomfield, H. ; Hal, R. van - \ 2011
MEFEPO - 88
visserijbeheer - governance - ecosysteembeheer - operationeel onderzoek - duurzaamheid (sustainability) - strategisch management - visserijbeleid - besluitvorming - participatie - noordzee - atlantische oceaan - fishery management - ecosystem management - operations research - sustainability - strategic management - fishery policy - decision making - participation - north sea - atlantic ocean
Since the reform of the EU Common Fisheries Policy in 2002, effort has been devoted to addressing the governance, scientific, social and economic issues required to introduce an ecosystem approach to fisheries management (EAFM) in Europe. Fisheries management needs to support the three pillars of sustainability (ecological, social and economic) and Fisheries Ecosystem Plans (FEPs) have been developed as a tool to assist managers considering the ecological, social and economic implications of their decision. Building upon previous studies (e.g. the FP5-funded European Fisheries Ecosystem Plan project), the core concept of the Making the European Fisheries Ecosystem Plan Operational (MEFEPO) project is to deliver operational frameworks (FEPs) for three regional seas. The project focus is on how best to make current institutional frameworks responsive to an EAFM at regional and pan-European levels in accordance with the principles of good governance. The regional seas selected for the project are the North Sea (NS), North Western Waters (NWW) and South Western Waters (SWW) RAC regions. The aim of this work package (WP5) was to develop operational objectives to achieve the ecological objectives identified for the 3 regional seas in WP2. This report describes the development and implementation of a transparent and formal process that should lead to identification of the “best” operational management strategies for an EAFM, based on sound scientific information and stakeholder involvement (e.g. regional industry groups, citizen groups, managers and other interest groups).
Blauwdruk voor Business Intelligence in de sierteelt
Anonymous, - \ 2010
S.l. : Royal Lemkes Group [etc.] - 26
tuinbouw - productiestructuur - bedrijfsvoering - optimalisatiemethoden - operationeel onderzoek - sierteelt - productieprocessen - logistiek - bedrijfsmanagement - ketenmanagement - horticulture - production structure - management - optimization methods - operations research - ornamental horticulture - production processes - logistics - business management - supply chain management
Het doel van Business Intelligence is het verbeteren van de effectiviteit en efficiëntie van ketenprocessen. Oftewel het verbeteren van de dagelijkse gang van zaken. Operationele Business Intelligence zou moeten bijdragen aan het doorvoeren van verbeteringen op verschillende gebieden, zoals tijdwinst, een hoger kwaliteitsniveau, reductie van transactiekosten, een betere beladingsgraad van vrachtwagens, reductie van ransportkilometers en een hogere responsiviteit in de keten.
Verbetering kuubskist : Energie-efficiënt drogen in een half(1/2)-laagssysteem
Wildschut, J. ; Sapounas, A. ; Wit, P. de; Bisschops, B. - \ 2010
Lisse : PPO Bloembollen en Bomen - 44
bloembollen - kratten - drogen - luchtstroming - optimalisatiemethoden - operationeel onderzoek - energiebesparing - ornamental bulbs - crates - drying - air flow - optimization methods - operations research - energy saving
Op basis van eerdere testen is het ontwerp van een alternatieve kuubskist naar een idee van Peter de Wit (bloembollenbedrijf N.N.J. de Wit/Nord Lommerse) d.m.v. CFD(modellering verbeterd. De 2 dwars op het palletkanaal ongeveer halverwege de kisthoogte geplaatste buizen van hetzelfde geperforeerde materiaal als de kistbodem zijn hierbij 10 cm hoger en 2,5 cm meer naar binnengeplaatst. Om ook tussen de buizen de luchtstroom te verbeteren zijn de perforaties in het bovenste en onderste kwadrant van de buizen gesloten. De resultaten samengevat in 6 punten op een poster ' Alternatieve kuubskist' zijn: Gelijkmatiger luchtverdeling over de kisten, kortere opstartfase van het droogproces, lagere weerstand en daardoor hoger debiet, 30% eerder sneldroog, kans op ziektes kleiner, 17 % op gas en 34% op elektra bespaard.
Proceedings of the Toulouse Global Optimization workshop : TOGO10 : Toulouse, France, August-September 2010
Cafieri, S. ; G.-Tóth, B. ; Hendrix, E.M.T. ; Liberti, L. ; Messine, F. - \ 2010
Toulouse : ENSEEIHT - 166
optimalisatie - optimalisatiemethoden - operationeel onderzoek - werkplaatsen - optimization - optimization methods - operations research - workshops
Meting van ruimtelijke verdeling van temperatuur en RV met behulp van draadloze minisensoren (Smart Dust). Deel 3: Metingen bij praktijkbedrijven in verschillende seizoenen
Balendonck, J. ; Os, E.A. van; Schoor, R. van der; Tuijl, B.A.J. van; Keizer, L.C.P. - \ 2010
Wageningen : Wageningen UR Glastuinbouw (Rapport / Wageningen UR Glastuinbouw 311) - 74
kassen - temperatuur - vochtigheid - sensors - seizoenen - operationeel onderzoek - tests - klimaatregeling - glastuinbouw - meetsystemen - draadloze sensornetwerken - energiebesparing - greenhouses - temperature - humidity - seasons - operations research - air conditioning - greenhouse horticulture - measurement systems - wireless sensor networks - energy saving
Beschrijving van de metingen bij praktijkbedrijven in verschillende seizoenen.
Introduction to Nonlinear and Global Optimization
Hendrix, E.M.T. ; Tóth, B. - \ 2010
Germany : Springer (Springer Optimization and Its Applications 37) - ISBN 9780387886695 - 208
wiskunde - operationeel onderzoek - programmeren - differentiaalmeetkunde - mathematics - operations research - programming - differential geometry
This self-contained text provides a solid introduction to global and nonlinear optimization, providing students of mathematics and interdisciplinary sciences with a strong foundation in applied optimization techniques. The book offers a unique hands-on and critical approach to applied optimization which includes the presentation of numerous algorithms, examples, and illustrations, designed to improve the reader{u2019}s intuition and develop the analytical skills needed to identify optimization problems, classify the structure of a model, and determine whether a solution fulfills optimality conditions. Key features of "Introduction to Nonlinear and Global Optimization": - Offers insights into relevant concepts such as "regions of attraction", "branch-and-bound", and "cross-cutting" methods as well as many other useful methodologies. -Exhibits numerical examples and exercises developing the reader{u2019}s familiarity with the terminology and algorithms that are frequently encountered in scientific literature. - Presents various heuristic and stochastic optimization techniques demonstrating how each be applied to a variety of models from biology, engineering, finance, chemistry, and economics. This book is intended to serve as a primary text in an advanced undergraduate or graduate course focusing on nonlinear and global optimization and requires an understanding of basic calculus and linear algebra.
Bedrijfsbegeleiding bij M. chitwoodi-besmetting in Noord-Holland
Visser, J.H.M. - \ 2009
Kennisakker.nl 2009 (2009)18 feb..
pootaardappelen - vermeerderingsmateriaal - daucus - erwten - scorzonera - meloidogyne chitwoodi - operationeel onderzoek - bemonsteren - akkerbouw - seed potatoes - propagation materials - peas - operations research - sampling - arable farming
Het maïswortelknobbelaaltje, Meloidogyne chitwoodi (MC), veroorzaakt grote economische schade in talloze gewassen, zoals o.a. poot- en consumptieaardappelen, erwten, peen en schorseneer. Het bedrijfsbegeleidingsproject heeft tot doel begeleiding te bieden aan met Meloidogyne chitwoodi besmette bedrijven, zodanig dat de economische gevolgen zo klein mogelijk blijven en dat de uitstraling voor het gehele gebied beperkt blijft.
Methods for robustness programming
Olieman, N.J. - \ 2008
University. Promotor(en): Paul van Beek, co-promotor(en): Eligius Hendrix. - S.l. : S.n. - ISBN 9789085048763 - 176
wiskunde - operationeel onderzoek - schatting - programmeren - monte carlo-methode - computerwiskunde - mathematics - operations research - estimation - programming - monte carlo method - computational mathematics
Robustness of an object is defined as the probability that an object will have properties as required. Robustness Programming (RP) is a mathematical approach for Robustness estimation and Robustness optimisation. An example in the context of designing a food product, is finding the best composition of ingredients such that the product is optimally safe and is satisfying all specifications. Another example is the investment in a portfolio of stock market shares. The number of shares to invest in is typically a controllable factor. The future shares prices and resulting portfolio return are typically uncontrollable factors. It is interesting to find the composition of shares for which the probability of reaching a predefined target return is as high as possible.
In this research alternative methods for Robustness Programming are developed with favourable optimisation properties for finding a design with a Robustness as high as possible. Some of these methods are generally applicable, while other methods use specific problem characteristics. A framework for Robustness Programming is developed for modelling design problems from a wide application area and to select the applicable RP methods for such design problems.
Balans gezocht voor meerproductie in gesloten teelt (interviews met o.a. Filip van Noort en Leo Marcelis)
Kamminga, H. ; Noort, F.R. van; Marcelis, L.F.M. - \ 2008
Vakblad voor de Bloemisterij 63 (2008)1. - ISSN 0042-2223 - p. 40 - 41.
kassen - gesloten systemen - technologie - cultuurmethoden - optimalisatie - operationeel onderzoek - klimaatregeling - milieubeheersing - glastuinbouw - greenhouses - closed systems - technology - cultural methods - optimization - operations research - air conditioning - environmental control - greenhouse horticulture
Een gesloten kas vergt hoge investeringen. Het is daarom niet voldoende dat er planten in kunnen groeien, ze moeten er ook beter in groeien. De vier klimaatfactoren licht, temepratuur, CO2 en vocht moeten in balans zijn voor een hogere productie in een gesloten kas. In theorie lijkt het te kunnen, maar het zoeken naar de optimale omstandigheden voor de praktijk zijn nog maar net begonnen.
State-of-the-Art bewaarsysteem tulpenbollen
Wildschut, J. ; Kok, M. ; Kreuk, F. - \ 2007
Lisse : PPO Bloembollen en Bomen - 30 p.
bloembollen - tulpen - energiebesparing - opslag met klimaatbeheersing - operationeel onderzoek - drogen - opslagkwaliteit - ornamental bulbs - tulips - energy saving - controlled atmosphere stores - operations research - drying - storage quality
Het State-of-the-Art systeem voor het bewaren van tulpenbollen bestaat uit 4 componenten waarvan in eerder onderzoek is aangetoond dat deze ieder afzonderlijk veel energie kunnen besparen: 1) De moderne systeemwand met afgeronde uitblaasopeningen en een interne schuine wand en 2) de aangepaste kuubskist met afgeschuinde hoekbalken en smallere bodemlatten reduceren de luchtweerstand en verhogen daardoor het debiet, 3) verminderde circulatie met frequentieregelaars vermindert het kWh-verbruik van de ventilatoren en 4) ethyleengestuurde ventilatie vermindert het gasverbruik en verbetert daarnaast de kwaliteit van de bollen. Doelstelling van het State-of-the-Art project is om te onderzoeken hoe op praktijkbedrijven de combinatie van deze componenten plus sturing door de klimaatcomputer, uitpakt in termen van energie- en kostenbesparing en om het ‘State-of-the-Art’-systeem te demonstreren aan de doelgroep: telers en broeiers van tulpenbollen.
Energiestroom Lelie
Wildschut, J. ; Kok, M. - \ 2007
Lisse : PPO Bloembollen en Bomen - 18
bloembollen - lelies - opslag met klimaatbeheersing - landbouwbedrijfsgebouwen - energiegebruik - energiebesparing - operationeel onderzoek - ornamental bulbs - lilies - controlled atmosphere stores - farm buildings - energy consumption - energy saving - operations research
Doelstellingen van dit onderzoek zijn de achtergronden in kaart te brengen van het (toegenomen) elektraverbruik op lelieteeltbedrijven om zo een duidelijk beeld van de energiestromen te krijgen. Hierdoor komen pieken en knelpunten van het energieverbruik in beeld zodat er gericht gezocht kan worden naar oplossingen om het energieverbruik te verminderen en de energiekosten te verlagen.
Zicht op Logistiek; Model-Leren van AgriFood Ketennetwerken
Vorst, J.G.A.J. van der - \ 2007
Wageningen : Wageningen Universiteit - 17
voedselketens - operationeel onderzoek - verse producten - logistiek - ketenmanagement - food chains - operations research - fresh products - logistics - supply chain management
Decision Science : theory and applications
Claassen, G.D.H. ; Hendriks, T.H.B. ; Hendrix, E.M.T. - \ 2007
Wageningen, The Netherlands : Wageningen Academic Publishers (Mansholt publication series vol. 2) - ISBN 9789086860012 - 450
besluitvorming - kwantitatieve technieken - optimalisatiemethoden - lineair programmeren - integer programmeren - dynamisch programmeren - simulatie - operationeel onderzoek - kwantitatieve methoden - beslissingsondersteunende systemen - niet-lineair programmeren - decision making - quantitative techniques - optimization methods - linear programming - integer programming - dynamic programming - simulation - operations research - quantitative methods - decision support systems - nonlinear programming
Decision science is the discipline that is concerned with the development and applications of quantitative methods and techniques to support decision making processes. This extensively revised edition of two former versions of the book discusses the general principles and often used optimisation techniques such as linear programming, integer programming, dynamic programming, non-linear programming, network theory, simulation and stochastic programming. This book aims to fill in the gap between theory and practice. It discusses the theoretical background of important quantitative methods and techniques as well as how they can be applied to practical decision making problems. Therefore, the modeling process is illustrated with examples of firms, consumers, governments and other non-profit organisations in agriculture related sectors. The authors have used their vast didactical experience to find a proper balance between mathematical exactness, knowledge and readability on the one hand and offer understanding, insights and applicability of the subjects on the other hand. The book is therefore an essential asset in introductory courses on decision science in undergraduate, postgraduate and research programmes.
Game theory at work: OR models and algorythms to solve multi-actor heterogeneous decision problems
Sáiz Pérez, M.E. - \ 2007
University. Promotor(en): Adrie Beulens; Jack van der Vorst, co-promotor(en): Eligius Hendrix. - [S.l.] : S.n. - ISBN 9789085047698 - 141
speltheorie - modellen - algoritmen - optimalisatiemethoden - operationeel onderzoek - beslissingsmodellen - modelleren - game theory - models - algorithms - optimization methods - operations research - decision models - modeling
Key words: Game theory, operations research, optimisation methods, algorithms. The objective of this thesis is to explore the potential of combining Game Theory (GT) models with Operations Research (OR) modelling. This includes development of algorithms to solve these complex OR models for different empirical situations. The challenge is to get GT “at work” by applying such models and techniques to practical cases. Four different cases with a challenge on the development of algorithms are studied. A first case illustrates a multiple coalition formation game in which membership rules and different transfer schemes are described. Given the GT model and the OR model, the goal is to develop methods for checking stability of coalition structures. A new mathematical programming formulation, crucial for the development of the algorithms, is elaborated. Available data is used to determine which stable coalitions appear and which procedures (transfer schemes) can be used to make coalitions stable. Also the influence of membership rules (whether actors are free to become a member) is investigated. Main conclusion is that transfer schemes are useful to be implemented to obtain stable coalitions. Moreover, different membership rules, e.g. veto or majority voting of current members, generate different results with and without transfer schemes. A second case studies a model of coalition formation in politics with n parties trying to form a government. Given the number of parties n and policy dimension m (number of items), computational algorithms are developed to compute all possible majority coalitions and preferences of parties over those coalitions. Application to Dutch data and theoretical examples leads to testing of hypotheses with surprising results with respect to coalition formation such as: being a first mover is not necessarily advantageous, being less flexible is not necessarily advantageous, forming a minimal winning coalition is not necessarily advantageous. A third case describes a two-stage location-quantity game where n > 2 firms are competing on m > 2 markets. The space where the firms can locate are nodes on a network. Analytical solutions for the supplying decisions and properties for determining the number of suppliers to each market are derived. In finding the equilibria, a complete enumeration algorithm and a local search algorithm are used. Two cases are elaborated to illustrate the procedures and the analytical results. The last case deals with a competitive facility location problem in which the concept of Stackelberg leader-follower problem is applied. The follower problem and leader problem are global optimisation problems. Branch-and-Bound (B&B) algorithms that guarantee to find the optimum of both problems are designed.
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