Research

My background is in Queueing Theory, Applied Probability, and Stochastic Operations Research. In my PhD I studied strategies for optimizing travel times in warehousing carousels. From 2004 I shifted the application area to healthcare logistics, joining the group of colleagues that now forms the Centre for Healthcare Operations Improvement & Research (CHOIR). At the same time, I started my own research line on probabilistic analysis of algorithms for complex networks, such as the Google PageRank algorithm for ranking of web search results. Part of this research was funded by the NWO Meervoud grant, 2005-2009. This research also gave rise to other interesting projects, such as solving the Hamiltonian Cycle Problem with Markov chains. Below is a more detailed description of my current research.

Algorithms for Complex Stochastic Networks

Typical examples of complex network include world wide web, scientific citations, and (on-line) social networks. In the last 10-15 years such networks attracted enormous attention because of their increasing importance in our daily life. My research is goal is mathematically rigorous analysis of network algorithms. A most prominent example of a network algorithm the Google PageRank that ranks web pages by quality and quantity of incoming links. My research includes several topics:

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analysis of ranking schemes and centrality measures in random graphs;

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evaluation of network mixing patterns; quick detection of network structure;

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analysis of bibliometric indicators for evaluating research performance;

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ranking algorithms with application to web, wikipedia, voting and recommendation systems.

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In future I would like to study the role of topology in complex service systems such as internet and power grids.

Markov Chains and the Hamiltonian Cycle Problem

Hamiltonian Cycle Problem (HCP) is one of the most intriguing problems in Combinatoric Optimization. I study this problem from the point of view of random walks on graphs. From that prospective, the problem is in finding a perturbed random walk with minimum variability. This is a joint research with several colleagues in Australia.

Health Care Logistics

Like in many countries, the healthcare institutions in the Netherlands are facing major challenges. Healthcare expenditures are increasing every year, the public is demanding higher quality of care, the population is ageing, the range of treatments is growing. My research is on strategic hospital planning in Dutch hospitals, in particular, I work on optimal utilization of hospital resources and reducing the patients’ waiting time. This is a part of the vast research on health care logistics at the Centre for Healthcare Operations Improvement & Research (CHOIR). Below are my recent projects that have been implemented in hospitals.

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Scheduling of appointments for children with neuromuscular disorders. Amsterdam Medical Centre, 2010-2011.

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Preparation of chemotherapy drugs: planning policy for reduced waiting times. The Netherlands Cancer Institute, 2010.

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Planning and scheduling of semi-urgent surgeries in neurology. Leiden University Medical Center, 2009-2010.