Agroforestry in the Nijmegen-area: visioning, sharing, designing

N/

The use of S&T indicators in science policy: Dutch experiences and theoretical perspectives from policy analysis

The relation between bibliometrics and science policy remains underdeveloped. Relevance of new methods to produce indicators is easily claimed, but often without real insight in the policy processes. Drawing on experiences with the use of S&T indicators in science policy in the Netherlands and on principal-agent theory, I develop an analytical perspective which enbles to assess the role of S&T indicators in science policy. It is argue that the use of S&T indicators can only be understood well if one takes the socio-political context with its specific dynamics and rationalities into account

Consistent nonparametric Bayesian inference for discretely observed scalar diffusions

We study Bayes procedures for the problem of nonparametric drift estimation for one-dimensional, ergodic diffusion models from discrete-time, low-frequency data. We give conditions for posterior consistency and verify these conditions for concrete priors, including priors based on wavelet expansions.Comment: Published in at http://dx.doi.org/10.3150/11-BEJ385 the Bernoulli (http://isi.cbs.nl/bernoulli/) by the International Statistical Institute/Bernoulli Society (http://isi.cbs.nl/BS/bshome.htm

Bayesian estimation of discretely observed multi-dimensional diffusion processes using guided proposals

Estimation of parameters of a diffusion based on discrete time observations poses a difficult problem due to the lack of a closed form expression for the likelihood. From a Bayesian computational perspective it can be casted as a missing data problem where the diffusion bridges in between discrete-time observations are missing. The computational problem can then be dealt with using a Markov-chain Monte-Carlo method known as data-augmentation. If unknown parameters appear in the diffusion coefficient, direct implementation of data-augmentation results in a Markov chain that is reducible. Furthermore, data-augmentation requires efficient sampling of diffusion bridges, which can be difficult, especially in the multidimensional case. We present a general framework to deal with with these problems that does not rely on discretisation. The construction generalises previous approaches and sheds light on the assumptions necessary to make these approaches work. We define a random-walk type Metropolis-Hastings sampler for updating diffusion bridges. Our methods are illustrated using guided proposals for sampling diffusion bridges. These are Markov processes obtained by adding a guiding term to the drift of the diffusion. We give general guidelines on the construction of these proposals and introduce a time change and scaling of the guided proposal that reduces discretisation error. Numerical examples demonstrate the performance of our methods

Perinatal mortality in the Netherlands. Backgrounds of a worsening international ranking

Perinatal mortality rates have dropped sharply in the past few decades, in the Netherlands as well as in all other European countries. However, as the decrease has generally slowed down since the 1980s, the Netherlands has lost its prominent position in the international ranking of countries with favourable perinatal mortality rates. This lower ranking is not only the result of the dialectics of progress, but also the consequence of a relatively restrained use of antenatal diagnostics. In addition, the Netherlands is among the European countries scoring highest on a number of important risk factors. This article examines the effect on perinatal mortality rates of known risk factors, in particular the presence of non-western foreigners, multiple births and older mothers. With respect to the latter factor, it is concluded that children of older mothers run a significantly higher risk of foetal mortality, whereas babies of young mothers (including women in their early twenties) run a higher risk of infant mortality. For babies of non-western mothers, infant mortality rates are higher, although there are substantial differences between ethnic backgrounds. First week mortality is most unfavourable for Surinamese and Antillean/Aruban children, and post-neonatal mortality is highest among Turkish and Moroccan babies. The fact that relatively many non-western foreigners from countries with relatively high risks of perinatal mortality have settled in the Netherlands, is one of the reasons for the fall in the international ranking. Lastly, the increase in the number of multiple births has been stronger in the Netherlands than in most other countries. The higher incidence of assisted reproduction explains most of this increase.ethnicity, foetal mortality, infant and child mortality, mortality, multiple births, neonatal mortality, perinatal mortality, Peristat, risk factors

Simulation of elliptic and hypo-elliptic conditional diffusions

Suppose $X$ is a multidimensional diffusion process. Assume that at time zero the state of $X$ is fully observed, but at time $T>0$ only linear combinations of its components are observed. That is, one only observes the vector $L X_T$ for a given matrix $L$. In this paper we show how samples from the conditioned process can be generated. The main contribution of this paper is to prove that guided proposals, introduced in Schauer et al. (2017), can be used in a unified way for both uniformly and hypo-elliptic diffusions, also when $L$ is not the identity matrix. This is illustrated by excellent performance in two challenging cases: a partially observed twice integrated diffusion with multiple wells and the partially observed FitzHugh-Nagumo model

Development of PV powered consumer products using future scenarios

Given the high potential of PV technology to reduce the environmental impact of electricity use of consumer products, it would be worthwhile to advance the application of PV systems in mass produced products. To date this field of application has been explored only to a limited extent. For this reason the developers of consumer products, the industrial designers, might be unaware of the possibilities of product-integrated PV systems [1][2]. Their focus on the utility of consumer products might have an added value to existing R&D of PV technology which emphasizes on increased performance and decreased production cost. In the nearby future integration of both points of view might be important to better integrate PV cells in consumer products. Therefore, in this paper, we will assess industrial product design of integrated PV technology in the context of future scenarios. In our project about 25 product designers have conceptually designed products with integrated flexible PV cells within a future scenario. By observing the resulting cases we can evaluate how the design process was established in the framework of integrated technology design, the product phase model and future scenarios. The PV-powered products that will be evaluated are an electronic book, an information bracelet, a floating platform, sports garment and a robotic monitoring device. Each product is supported by visual materials such as renderings and an explanation of the design process based on scenarios