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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.

Quantitative Methods

Mostrando recursos 1 - 20 de 393

  1. Why do firms save cash from cash flows? Evidence from firm-level estimation of cash-cash flow sensitivities

    D'ESPALLIER, Bert; HUYBRECHTS, Jolien; Schoubben, Frederiek
    We construct firm-level estimates for the cash flow sensitivity of cash (CCFS) by modelling heterogeneous slopes in reduced-form cash equations. This approach allows identifying firms with a high, low or even negative savings propensity. We find that high CCFS firms have higher income variation, suggesting cash buffering is triggered by income shocks. High CCFS firms do not suffer from financing constraints measured by a wide selection of indicators. Our results suggest that the CCFS is not an adequate indicator to capture financing constraints. Rather, a higher CCFS indicates smoothing of income fluctuations by installing a cash buffer that successfully prevents...

  2. Bayesian inference for transportation origin-destination matrices: the Poisson-inverse Gaussian and other Poisson mixtures

    PERRAKIS, Konstantinos; KARLIS, Dimitris; COOLS, Mario; JANSSENS, Davy
    Transportation origin-destination analysis is investigated through the use of Poisson mixtures by introducing covariate-based models which incorporate different transport modelling phases and also allow for direct probabilistic inference on link traffic based on Bayesian predictions. Emphasis is placed on the Poisson-inverse Gaussian model as an alternative to the commonly used Poisson-gamma and Poisson-log-normal models. We present a first full Bayesian formulation and demonstrate that the Poisson-inverse Gaussian model is particularly suited for origin-destination analysis because of its desirable marginal and hierarchical properties. In addition, the integrated nested Laplace approximation is considered as an alternative to Markov chain Monte Carlo sampling...

  3. Adapting inventory models for handling various payment structures using net present value equivalence analysis

    BEULLENS, Patrick; JANSSENS, Gerrit
    Classic inventory models use average cost functions. It is generally accepted that these models should account for the time value of money. They do so not by considering the timing of cash-flows, but by including opportunity costs. The Net Present Value (NPV) framework has long been used to compare these models with. We formalise NPV Equivalence Analysis (NPVEA) under various payment structures, and apply it to a few classic inventory models. While taking the linear approximation is typically part of the process to find equivalence, the essence is to disregard the parameters of a classic inventory model but instead start...

  4. The use of process mining in a business process simulation context: overview and challenges

    MARTIN, Niels; DEPAIRE, Benoit; CARIS, An
    This paper focuses on the potential of process mining to support the construction of business process simulation (BPS) models. To date, research efforts are scarce and have a rather conceptual nature. Moreover, publications fail to explicit the complex internal structure of a simulation model. The current paper outlines the general structure of a BPS model. Building on these foundations, modeling tasks for the main components of a BPS model are identified. Moreover, the potential value of process mining and the state of the art in literature are discussed. Consequently, a multitude of promising research challenges are identified. In this sense,...

  5. Innovation, competition and firm performance: An econometric analysis on the Dutch pharmaceutical sector

    Sanyal, Shreosi
    This study mainly deals with the contemporaneous relation between innovation, competition and firm performance, conditioned by various firm-level determinants, for the Dutch pharmaceutical industry. Our analysis encompasses R&D investment and patents as the essential indicators of innovation; and investigates on their plausible linkage with competition, firm size, firm age, capital intensity and other variables, that eventually affect the productivity and growth in this knowledgeintensive industry. In addition to a comprehensive theoretical exploration, a number of empirical investigations are performed on a firm-level panel database for the Netherlands’ pharmaceuticals. In this PhD dissertation, chapter 1 deals with the theoretical overview and...

  6. Integrated inventory-transportation with common carrier freight charges

    Suwandechochai, Rawee; Janssens, Gerrit K.
    Inventory management models aim to find an optimal solution in terms of minimal costs by proposing decisions on delivery quantities using data on order quantity purchasing costs and holding costs. Goods have to be transported from the supplier to the customer and the transport (freight charge) cost can be included in various ways. Some production companies make use of a private carrier, offering transport services only for one or a few companies. Most companies make use of the services of a common carrier, which offers its transport service to whatever customer in need for transporting goods. A common carrier offers...

  7. Optimisation of vessel journeys for oil products distribution

    HOANG, Thi Minh Ha; Janssens, Gerrit K.
    The research deals with a routing and scheduling problem of specialized vessels carrying oil products. A heterogeneous fleet transports the products from several loading ports to several discharging ports. Time windows are involved on the discharging side due to production and storage plans, and on the loading side as a result of negotiations with customers. Demand may be delivered by more than one vessel. The routing and scheduling problem is formulated as a mixed-integer programming problem. It includes information and constraints about the supply and demand, but also about the vessels, the vessel routes, and the ports and their restrictions.

  8. Generating Artificial Event Logs with Sufficient Discriminatory Power to Compare Process Discovery Techniques

    JOUCK, Toon; Depaire, Benoit
    Past research revealed issues with artificial event data used for comparative analysis of process mining algorithms. The aim of this research is to design, implement and validate a framework for producing artificial event logs which should increase discriminatory power of artificial event logs when evaluating process discovery techniques.

  9. Ruimtelijke specialisatie en clustering van industriegroepen en de productiviteitsgroei in sectoren in Limburg in kaart gebracht


  10. Identifying local determinants of destination choices of international immigrants to the Madrid metropolitan area

    Peeters, Ludo; Chasco, Coro
    We examine the local determinants of destination choices of foreign immigrants to the Madrid metro area using data for 2005 and 2009 from the Spanish annual municipal-level registers of inhabitants. Taking advantage of the equivalence relation between conditional logit and Poisson, we estimate a location-choice model using the Poisson fixed-effects estimator. Origin-destination fixed effects are incorporated to account for the persistent spatial structure of the immigrants’ settlement patterns and to control for potential violations of the independence of irrelevant alternatives (IIA) assumption. The Poisson regression model is estimated for seven different groups of immigrants according to world regions or countries...

  11. Real-Time Crash Risk Prediction Models using Loop Detector Data for Dynamic Safety Management System Applications

    Pirdavani, Ali; Magis, Maarten; De Pauw, Ellen; Daniels, Stijn; Bellemans, Tom; Brijs, Tom; Wets, Geert
    There is a growing trend in development and application of real-time crash risk prediction models within dynamic safety management systems. These real-time crash risk prediction models are constructed by associating crash data with the real-time traffic surveillance data, collected by loop detectors. The objective of this paper is to develop a real-time prediction model that will potentially be utilized within safety management systems. This model aims to predict the traffic safety condition of a motorway. Given that the dependent variable (i.e. traffic safety condition) is considered dichotomous (“no-crash” or “crash”), the binary logistic regression technique is selected for model development....

  12. Application of a Rule-Based Approach in Real-Time Crash Prediction Model Development for Motorways

    Pirdavani, Ali; De Pauw, Ellen; Daniels, Stijn; Magis, Maarten; Brijs, Tom; Bellemans, Tom; Wets, Geert
    There is a growing trend in development and application of real-time crash prediction models within dynamic safety management systems. These real-time crash prediction models are constructed by associating crash data with the real-time traffic surveillance data (e.g. collected by loop detectors). The crash and traffic data used in this study were collected between June 2009 and December 2011 on a part of the E313 motorway in Belgium between Geel-East and Antwerp-East exits, on the direction towards Antwerp. The main objective of this paper is to develop a real-time prediction model that will potentially be utilized within traffic management systems. This...

  13. Modeling Personal Exposure to Air Pollution with AB2C: Environmental Inequality

    DONS, Evi; KOCHAN, Bruno; BELLEMANS, Tom; WETS, Geert; INT PANIS, Luc
    The AB2C model (Activity-Based modeling framework for Black Carbon exposure assessment) was developed to assess personal exposure to air pollution, more specifically black carbon. Currently the model calculates exposure in Flanders, an urbanized region in Western Europe. This model is characterized by the use of time-activity patterns, and air pollution concentrations with a high spatial and temporal resolution, including indoors and in the transport microenvironment. This model can be used for disaggregated exposure assessment or the evaluation of policy scenarios. In this paper, exposure of people from a lower socioeconomic class (SEC) is compared to the exposure of people from...

  14. Integrating GIS and Feathers: A Conceptual Design

    Cho, Sungjin; Bellemans, Tom; Janssens, Davy; Wets, Geert
    This study proposes integrating GIS and FEATHERS in order to improve the capability of data management, spatial analysis and visualization in the model framework. GIS provides geodatabase for effectively storing and edit (non-)spatial data, useful functions of spatial analysis for defining spatial interactions between phenomena simulated by the modeling system, and interactive visualization tools. Thus, this study mainly focuses on three topics: i) why FEATHERS needs a GIS module, ii) how the GIS module is designed, and iii) what functions can be supported by the GIS module in the FEATHERS system. Moreover, we overview some transportation software adopting GIS to...

  15. A Field Study on the Use of Process Mining of Event Logs as an Analytical Procedure in Auditing

    JANS, Mieke; Alles, Michael G.; Vasarhelyi, Miklos A.
    There is a large body of accounting research literature examining the use of analytical procedures by auditors and proposing either new types of analytical procedures or more effective ways of implementing existing procedures. In this paper, we demonstrate using procurement data from a leading global bank the value added in an audit setting of a new type of analytical procedure: process mining of event logs. In particular, using process mining, we are able to identify numerous transactions that we consider to be audit-relevant information, including payments made without approval, violations of segregation of duty controls, and violations of company-specific internal...

  16. Towards a General Framework for Business Tests

    SWENNEN, Marijke; DEPAIRE, Benoit; JANS, Mieke; VANHOOF, Koen
    Testing and controlling business processes, activities, data and results is becoming increasingly important for companies. Based on the literature, business tests can be divided into three domains, i.e. performance, risk and compliance and separate domain-specific frameworks have been developed. These different domains and frameworks hint at some aspects that need to be taken into account when managing business tests in a company. In this paper we identify the most important concepts concerning business tests and their management and we provide a first conceptual business test model. We do this based on an archival research study in which we analyse business...

  17. Heterogeneous VRP review and conceptual framework

    Soonpracha, Kusuma; Mungwattana, Anan; Janssens, Gerrit K.; Manisri, Tharinee
    The purpose of this paper is to update recent research of the fleet size and mix vehicle routing problem (FSMVRP), the heterogeneous fleet vehicle routing problem (HFVRP), and the extensions in a form of a literature review. In this paper, four major components of the problem: classification, considerable input data characteristics, decision making approaches, and heuristic and meta-heuristics algorithms are discussed. The comprehensive overview of the heterogeneous vehicle routing problem which puts a special emphasis on robustness approach is concluded and demonstrated in a simplified structure which has never been presented before. New potential research areas resulting from the survey...

  18. Optimal policies for demand forecasting and inventory management of goods with intermittent demand

    Ramaekers, Katrien; Janssens, Gerrit
    Demand forecasting is one of the most crucial aspects of inventory management. For intermittent demand, i.e. demand peaks follow several periods of zero or low demands, accurate forecasting is difficult. A framework is developed to support inventory management decision making for intermittent demand. Several forecasting methods and inventory management policies are compared in this framework. Because mathematical models cannot accurately describe the complex system, a simulation model is built. To determine the best combination of a demand forecasting method and an inventory management policy, a continuous tabu search metaheuristic is developed to optimize the simulation model. Depending on the experimental...

  19. Quality of service in mobile ad hoc networks, carrying multimedia traffic

    NYAMBO, Benny; Janssens, Gerrit K.; Lamotte, Wim
    Mobile ad hoc networks (MANETs) have become an integral part of the ubiquitous computing and communication environment, providing new infrastructure for multimedia applications such as video phone, multimedia-on-demand, and others. In order to access multimedia information in a MANET, Quality of Service (QoS) needs to be considered, such as high success rate to access multimedia data, bounded end-to-end delay, security and others. Factors, like delay and jitter, bandwidth and throughput, are studied that affect quality of service in wireless mobile ad hoc networks. Various Quality of Service architectures on IEEE 802.11-based mobile ad hoc networks are discussed, concentrating on architectures...

  20. Exact and meta-heuristic approach for a general heterogeneous dial-a-ride problem with multiple depots

    Dial-a-ride problems are concerned with the design of efficient vehicle routes for transporting individual persons from specific origin to specific destination locations. In real-life this operational planning problem is often complicated by several factors. Users may have special requirements (e.g. to be transported in a wheelchair) while service providers operate a heterogeneous fleet of vehicles from multiple depots in their service area. In this paper, a general dial-a-ride problem in which these three real-life aspects may simultaneously be taken into account is introduced: the Multi-Depot Heterogeneous Dial-A-Ride Problem (MD-H-DARP). Both a three- and two-index formulation are discussed. A branch-and-cut algorithm...

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