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Repository of the University of Hasselt containing publications in the fields of statistics, computer science, information strategies and material from the Institute for behavioural sciences.

Research Institutes - Institute for Applied Economic Research (ITEO)

Mostrando recursos 1 - 20 de 27

  1. Electrical performance, reliability and microstructure of sub-45 nm copper damascene lines fabricated with TEOS backfill

    Leaming-Sphabmixay, K.; VAN OLMEN, Jan; Moon, K. J.; VANSTREELS, Kris; D'HAEN, Jan; Tokei, Z.; List, S.; Beyer, G.
    The fabrication of narrow Cu trenches using a conformal TEOS backfill approach is shown. Cu trenches with widths down to 3040 nm were achieved. With an adequate Ta-based PVD barrier and Cu seed layer scheme, narrow Cu lines with high yield were obtained. An increase of the electrical resistivity in the narrowest dimensions was observed as a result of the size effect. Electromigration assessment demonstrated that a bilayer TaN/Ta barrier outperforms the monolayer Ta barrier. Electron backscattering diffraction (EBSD) analysis was carried out to determine grain orientation and texture in narrow copper trenches. For the first time, EBSD data reveal...

  2. The global purchasing challenge : A look back and a look ahead

    MATTHYSSENS, Paul; PAUWELS, Pieter; QUINTENS, Lieven
    Despite the critical and still increasing importance of purchasing in a majority of globalizing industries, international purchasing remains a neglected research field. To date, it is largely unclear how the international context impacts on purchasing internationalization and organization, and how international purchasing brings return to the company. The aim of this special issue is to compile state-of-the-art research on the topic of global (international) purchasing. In this guest editorial, we look back at the roots of the field and look forward to the contributions in this special issue.

  3. Global purchasing : State of the art and research directions

    QUINTENS, Lieven; PAUWELS, Pieter; MATTHYSSENS, Paul
    This article presents a review of published research on global purchasing in the period 1990–2005. We rely on 123 articles to discuss the fields’ conceptual foundations and methodological approaches. We synthesize findings on the central phenomenon, its antecedents and consequences as well on the globalization process of purchasing. This review learns that the conceptual foundation of this field remains premature. Global purchasing research would benefit from a significant convergence in and formalization of its conceptual basis as well as from more explanatory and less descriptive empirical work.

  4. A technological contingency perspective on the dept and scope of international outsourcing

    Mol, M.J.; PAUWELS, Pieter; MATTHYSSENS, Paul
    In this study we present and test a technological contingency perspective on two dimensions of international outsourcing: depth and scope. The depth of international outsourcing refers to the ratio of foreign to total outsourcing. The scope of international outsourcing refers to the ratio of foreign to total outsourcing. The scope of international outsourcing captures the degree of psychic dispersion between the country of operations and the countries a firm is outsourcing to. Using multiple regression analysis on a sample of 189 Dutch firms, the effect of five technological contingency factors is measured: product innovation, technological and volume uncertainty, asset specificity,...

  5. A synthesis of fuzzy rule-based system verification

    Viaene, S; WETS, Geert; Vanthienen, J
    The verification of fuzzy rule bases for anomalies has received increasing attention these last few years. Many different approaches have been suggested and many are still under investigation. In this paper, we give a synthesis of methods proposed in literature that try to extend the Verification of classical rule bases to the case of fuzzy knowledge modeling, without needing a set of representative input. Within this area of fuzzy validation and verification (V&V) we identify two dual lines of thought leading to what is identified as static and dynamic anomaly detection methods. Static anomaly detection essentially tries to use similarity,...

  6. Analysis of company growth data using genetic algorithms on binary trees

    JANSSENS, Gerrit; Sorensen, K; LIMERE, Arthur; VANHOOF, Koen
    This paper investigates why some companies grow faster than others, by data mining a survey of a large number of companies in Flanders (the northern part of Belgium). Faster or slower average growth over a time period is explained by building a classification tree containing several categorical variables (both quantitative and qualitative). The technique used - called genAID - splits the population at different levels. It is inspired by the Automatic Interaction Detector (AID) technique to find trees that explain the variability in average growth but uses a genetic algorithm to overcome some of the drawbacks of AID. Classical AID...

  7. On the dreama and the action ... mainly on the practical complaint. Election analysis in the scope of a regional elite study

    CONINCKX, Daniel

  8. Freight transportation demand elasticities: a geographic multimodal transportation network analysis

    Beuthe, M; JOURQUIN, Bart; Geerts, JF; Ha, CKAN
    This paper presents direct and cross-elasticity estimates of the demands for three freight transportation modes: rail, road and inland waterways. They are computed for 10 different categories of goods with a detailed multimodal network model of Belgian freight transports. The model, which minimises the generalised cost of transportation tasks defined by O-D matrices, assigns traffic flows to the different modes, transport means and routes. Successive simulations with different relative costs permit the computation of specific are-elasticities. In contrast with the usual methodologies, the present methodology is not based on a statistical analysis of disaggregate data on actual modal choices and...

  9. External costs of the Belgian interurban freight traffic: a network analysis of their internalisation

    Beuthe, M; Degrandsart, F; Geerts, JF; JOURQUIN, Bart
    The strong expansion of freight road transports throughout Europe is an important source of congestion and pollution, as well as a cause of many accidents. To solve this problem will require the conjunction of many different remedies. One element of solution would be the promotion and substitution of transportation modes with less negative effects. This paper is focused on this solution. It presents some results obtained from a detailed GIS modelling of the Belgian multimodal freight transport network inserted within the overall trans-European network. It outlines the results of a simulation of the flows over the Belgian network in 1995...

  10. Simple association rules (SAR) and the SAR-based rule discovery

    Chen, GQ; Wei, Q; Liu, D; WETS, Geert
    Association rule mining is one of the most important fields in data mining and knowledge discovery in databases. Rules explosion is a problem of concern, as conventional mining algorithms often produce too many rules for decision makers to digest. Instead, this paper concentrates on a smaller set of rules, namely, a set of simple association rules each with its consequent containing only a single attribute. Such a rule set can be used to derive all other association rules, meaning that the original rule set based on conventional algorithms can be 'recovered' from the simple rules without any information loss. The...

  11. New heuristics for the fleet size and mix vehicle routing problem with time windows

    Dullaert, W; JANSSENS, Gerrit; Sorensen, K; Vernimmen, B
    In the Fleet Size and Mix Vehicle Routing Problem with Time Windows (FSMVRPTW) customers need to be serviced in their time windows at minimal costs by a heterogeneous fleet. In this paper new heuristics for the FSMVRPTW are developed. The performance of the heuristics is shown to be significantly higher than that of any previous heuristic approach and therefore likely to achieve better solutions to practical routing problems.

  12. Comparing complete and partial classification for identifying customers at risk

    BLOEMER, Johanna; BRIJS, Tom; VANHOOF, Koen; SWINNEN, Gilbert
    This paper evaluates complete versus partial classification for the problem of identifying customers at risk. We define customers at risk as customers reporting overall satisfaction, but these customers also possess characteristics that are strongly associated with dissatisfied customers. This definition enables two viable methodological approaches for identifying such customers, i.e. complete and partial classification. Complete classification entails the induction of a classification model to discriminate between overall dissatisfied and overall satisfied instances, where customers at risk are defined as overall satisfied customers who are classified as overall dissatisfied. Partial classification entails the induction of the most prevalent characteristics of overall...

  13. Data mining with genetic algorithms on binary trees

    Sorensen, K; JANSSENS, Gerrit
    This paper focuses on the automatic interaction detection (AID)-technique, which belongs to the class of decision tree data mining techniques. The AID-technique explains the variance of a dependent variable through an exhaustive and repeated search of all possible relations between the (binary) predictor variables and the dependent variable. This search results in a tree in which non-terminal nodes represent the binary predictor variables, edges represent the possible values of these predictor variables and terminal nodes or leafs correspond to classes of subjects. Despite of being self-evident, the AID-technique has its weaknesses. To overcome these drawbacks a technique is developed that...

  14. Building an association rules framework to improve product assortment decisions

    BRIJS, Tom; SWINNEN, Gilbert; VANHOOF, Koen; WETS, Geert
    It has been claimed that the discovery of association rules is well suited for applications of market basket analysis to reveal regularities in the purchase behaviour of customers. However today, one disadvantage of associations discovery is that there is no provision for taking into account the business value of an association. Therefore, recent work indicates that the discovery of interesting rules can in fact best be addressed within a microeconomic framework. This study integrates the discovery of frequent itemsets with a (microeconomic) model for product selection (PROFSET). The model enables the integration of both quantitative and qualitative (domain knowledge) criteria....

  15. Bankruptcy prediction using a data envelopment analysis

    CIELEN, Agnes; PEETERS, Ludo; VANHOOF, Koen
    There is a growing recognition that a variety of machine learning problems can be approached advantageously by tools from the field of optimization. In this paper we compare the classification performance of a linear programming model, a data envelopment (DEA) model and a rule induction (C5.0) model. In terms of accuracy and employment the DEA model outperforms the other models. (C) 2003 Elsevier B.V. All rights reserved.

  16. Customer-adapted coupon targeting using feature selection

    Buckinx, W; MOONS, Elke; Van den Poel, D; WETS, Geert
    The management of coupon promotions is an important issue for marketing managers since it still is the major promotion medium. However, the distribution of coupons does not go without problems. Although manufacturers and retailers are investing heavily in the attempt to convince as many customers as possible, overall coupon redemption rate is low. This study improves the strategy of retailers and manufacturers concerning their target selection since both parties often end up in it battle for customers. Two separate models are built: one model makes predictions concerning redemption behavior of coupons that are distributed by the retailer while another model...

  17. A multivariate Poisson mixture model for marketing applications

    BRIJS, Tom; KARLIS, Dimitris; SWINNEN, Gilbert; VANHOOF, Koen; WETS, Geert; Manchanda, P.
    This paper describes a multivariate Poisson mixture model for clustering supermarket shoppers based on their purchase frequency in a set of product categories. The multivariate nature of the model accounts for cross-selling effects between the purchases made in different product categories. However, for computational reasons, most multivariate approaches limit the covariance structure by including just one common interaction term, or by not including any covariance at all. Although this reduces the number of parameters significantly, it is often too simplistic as typically multiple interactions exist on different levels. This paper proposes a theoretically more complete variance/covariance structure of the multivariate...

  18. A tree based lack-of-fit test for multiple logistic regression

    MOONS, Elke; AERTS, Marc; WETS, Geert
    Several omnibus tests have been developed to assess the fit of a regression model. But many of these lack-of-fit tests focus on the simple regression setting. Here, we focus on multiple logistic regression. Pearson's well-known chi-square test statistic and the deviance statistic are no longer valid in the case that the model contains one or more continuous covariates. To overcome this difficulty, Hosmer and Lemeshow proposed a Pearson type statistic based on groups defined by the so-called deciles of risk. We propose a test statistic that is similar in approach to the Hosmer and Lemeshow statistic in that the observations...

  19. Mining navigation patterns using a sequence alignment method

    HAY, Birgit; WETS, Geert; VANHOOF, Koen
    In this article, a new method is illustrated for mining navigation patterns on a web site. Instead of clustering patterns by means of a Euclidean distance measure, in this approach users are partitioned into clusters using a non-Euclidean distance measure called the Sequence Alignment Method (SAM). This method partitions navigation patterns according to the order in which web pages are requested and handles the problem of clustering sequences of different lengths. The performance of the algorithm is compared with the results of a method based on Euclidean distance measures. SAM is validated by means of user-traffic data of two different...

  20. A Petri net model of a continuous flow transfer line with unreliable machines

    Sorensen, K; JANSSENS, Gerrit
    A production line is studied with several machines in series. The machines are separated with finite buffers. They can break down and have to be repaired. Production is assumed to be continuous, i.e. no individual products can be identified. Analytical models for such a system are scarce. Analytical results for the throughput can be obtained only under very restrictive assumptions. The study of longer transfer lines requires either approximation or simulation. A general Petri net model is developed for an n-machine (n - I)-buffer system. Rules to dress up the Petri net transitions are given. The automatic generation of a...

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