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Apeldoorn, Netherlands

Visschers J.,Statistics Netherlands | Adan I.,TU Eindhoven | Weiss G.,Haifa University
Queueing Systems | Year: 2012

We consider a memoryless single station service system with servers S = {m1,...,mK}and with job types C = {a,b...}. Service is skill-based, so that server mi can serve a subset of job types C(mi). Waiting jobs are served on a first-come-first-served basis, while arriving jobs that find several idle servers are assigned to a feasible server randomly. We show that there exist assignment probabilities under which the system has a product-form stationary distribution, and obtain explicit expressions for it. We also derive waiting time distributions in steady state. © 2012 The Author(s). Source

Edens B.,Statistics Netherlands | Edens B.,VU University Amsterdam | Hein L.,Wageningen University
Ecological Economics | Year: 2013

In spite of an increasing interest in environmental economic accounting, there is still very limited experience with the integration of ecosystem services and ecosystem capital in national accounts. This paper identifies four key methodological challenges in developing ecosystem accounts: the definition of ecosystem services in the context of accounting, their allocation to institutional sectors; the treatment of degradation and rehabilitation, and valuing ecosystem services consistent with SNA principles. We analyze the different perspectives taken on these challenges and present a number of proposals to deal with the challenges in developing ecosystem accounts. These proposals comprise several novel aspects, including (i) presenting an accounting approach that recognizes that most ecosystems are strongly influenced by people and that ecosystem services depend on natural processes as well as human ecosystem management; and, (ii) recording ecosystem services as either contributions of a private land owner or as generated by a sector 'Ecosystems' depending on the type of ecosystem service. We also present a consistent approach for recording degradation, and for applying monetary valuation approaches in the context of accounting. © 2013 Elsevier B.V. Source

Bekkers R.,TU Eindhoven | Bekkers R.,Dialogic | Bongard R.,Statistics Netherlands | Nuvolari A.,SantAnna School of Advanced Studies
Research Policy | Year: 2011

In the field of compatibility standards, an increasing number of companies claim to own so-called essential patents (i.e. those patents that are indispensable for designing and manufacturing products conforming to the standard). It is widely believed that the ownership of such patents is a very valuable bargaining tool in cross-license negotiations, while for non-producing firms such patents may result in a substantial stream of licensing revenues. In this paper we study the determinants of essential patent claims in compatibility standards. In particular, we assess the role of two main factors: the significance of the technological solution contained in the patent and the involvement of the applicant of the patent in the standardisation process. We examine the case of W-CDMA, one of the most successful standards in mobile telecommunications. We compare the patents claimed essential for this standard with a control group of randomly selected, unclaimed patents covering the same time period and technology classes. We find empirical evidence that both factors have significant impact on the probability that a patent is claimed as essential, but the involvement in the standardisation process is a stronger determinant than the technical value ('merit') of the patent. On the basis of our findings, we offer policy recommendations. © 2011 Elsevier B.V. All rights reserved. Source

Maes D.,Research Institute for Nature and Forest INBO | Isaac N.J.B.,Biological Records Center | Harrower C.A.,Biological Records Center | Collen B.,University College London | And 2 more authors.
Biological Journal of the Linnean Society | Year: 2015

IUCN Red Lists are recognized worldwide as powerful instruments for the conservation of species. Quantitative criteria to standardize approaches for estimating population trends, geographic ranges and population sizes have been developed at global and sub-global levels. Little attention has been given to the data needed to estimate species trends and range sizes for IUCN Red List assessments. Few regions collect monitoring data in a structured way and usually only for a limited number of taxa. Therefore, opportunistic data are increasingly used for estimating trends and geographic range sizes. Trend calculations use a range of proxies: (i) monitoring sentinel populations, (ii) estimating changes in available habitat, or (iii) statistical models of change based on opportunistic records. Geographic ranges have been determined using: (i) marginal occurrences, (ii) habitat distributions, (iii) range-wide occurrences, (iv) species distribution modelling (including site-occupancy models), and (v) process-based modelling. Red List assessments differ strongly among regions (Europe, Britain and Flanders, north Belgium). Across different taxonomic groups, in European Red Lists IUCN criteria B and D resulted in the highest level of threat. In Britain, this was the case for criterion D and criterion A, while in Flanders criterion B and criterion A resulted in the highest threat level. Among taxonomic groups, however, large differences in the use of IUCN criteria were revealed. We give examples from Europe, Britain and Flemish Red List assessments using opportunistic data and give recommendations for a more uniform use of IUCN criteria among regions and among taxonomic groups. © 2015 The Linnean Society of London. Source

Kramer D.,University of Amsterdam | Maas J.,VU University Amsterdam | Wingen M.,Statistics Netherlands | Kunst A.E.,University of Amsterdam
International Journal of Behavioral Nutrition and Physical Activity | Year: 2013

Background: Several neighbourhood elements have been found to be related to leisure-time walking and cycling. However, the association with neighbourhood safety remains unclear. This study aimed to assess the association of neighbourhood-level safety with leisure-time walking and cycling among Dutch adults.Methods: Data were derived from the national health survey (POLS) 2006-2009, with valid data on 20046 respondents residing in 2127 neighbourhoods. Multilevel logistic regression models were used to examine the association between neighbourhood-level safety (general safety and specific safety components: physical disorder, social disorder, crime-related fear, traffic safety) and residents' engagement in outdoor leisure-time walking and cycling for at least 30 minutes per week.Results: An increase in neighbourhood safety (both general safety and each of the safety components) was significantly associated with an increase in leisure-time cycling participation. Associations were strongest for general safety and among older women. In the general population, neighbourhood safety was not significantly associated with leisure-time walking. However, among younger and older adult men and lower educated individuals, an increase in general safety was associated with a decrease in leisure-time walking participation.Conclusions: In the Netherlands, neighbourhood safety appears to be related to leisure-time cycling but not to walking. Leisure-time cycling may best be encouraged by improving different safety components at once, rather than focusing on one safety aspect such as traffic safety. Special attention is needed for older women. © 2013 Kramer et al.; licensee BioMed Central Ltd. Source

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