Strategic options for the newspaper publishing companies.

Tevens verschenen als: Research Memorandum / METEOR, Universiteit Maastricht. - (RM04003)

On Sparsification for Computing Treewidth

We investigate whether an n-vertex instance (G,k) of Treewidth, asking whether the graph G has treewidth at most k, can efficiently be made sparse without changing its answer. By giving a special form of OR-cross-composition, we prove that this is unlikely: if there is an e > 0 and a polynomial-time algorithm that reduces n-vertex Treewidth instances to equivalent instances, of an arbitrary problem, with O(n^{2-e}) bits, then NP is in coNP/poly and the polynomial hierarchy collapses to its third level. Our sparsification lower bound has implications for structural parameterizations of Treewidth: parameterizations by measures that do not exceed the vertex count, cannot have kernels with O(k^{2-e}) bits for any e > 0, unless NP is in coNP/poly. Motivated by the question of determining the optimal kernel size for Treewidth parameterized by vertex cover, we improve the O(k^3)-vertex kernel from Bodlaender et al. (STACS 2011) to a kernel with O(k^2) vertices. Our improved kernel is based on a novel form of treewidth-invariant set. We use the q-expansion lemma of Fomin et al. (STACS 2011) to find such sets efficiently in graphs whose vertex count is superquadratic in their vertex cover number.Comment: 21 pages. Full version of the extended abstract presented at IPEC 201

Kernel Bounds for Structural Parameterizations of Pathwidth

Assuming the AND-distillation conjecture, the Pathwidth problem of determining whether a given graph G has pathwidth at most k admits no polynomial kernelization with respect to k. The present work studies the existence of polynomial kernels for Pathwidth with respect to other, structural, parameters. Our main result is that, unless NP is in coNP/poly, Pathwidth admits no polynomial kernelization even when parameterized by the vertex deletion distance to a clique, by giving a cross-composition from Cutwidth. The cross-composition works also for Treewidth, improving over previous lower bounds by the present authors. For Pathwidth, our result rules out polynomial kernels with respect to the distance to various classes of polynomial-time solvable inputs, like interval or cluster graphs. This leads to the question whether there are nontrivial structural parameters for which Pathwidth does admit a polynomial kernelization. To answer this, we give a collection of graph reduction rules that are safe for Pathwidth. We analyze the success of these results and obtain polynomial kernelizations with respect to the following parameters: the size of a vertex cover of the graph, the vertex deletion distance to a graph where each connected component is a star, and the vertex deletion distance to a graph where each connected component has at most c vertices.Comment: This paper contains the proofs omitted from the extended abstract published in the proceedings of Algorithm Theory - SWAT 2012 - 13th Scandinavian Symposium and Workshops, Helsinki, Finland, July 4-6, 201

Phase gratings for plasmon focusing

We report gratings structures realized for the creation of focused plasmons through noncollinear phasematching. The gratings are created on gold by focused ion beam milling and the plasmons were measured using phase sensitive photon scanning tunneling microscope (PSTM)

Engineered plasmon focusing on functional gratings

We report on the engineering of plasmon propagation and focusing by dedicated curved gratings and noncollinear phasematching. Gratings were created on gold by focused ion beam milling and plasmons were measured using phase sensitive PSTM

Overview CGMS and related tools

The main purpose of Crop Growth Monitoring System CGMS is to estimate the influence of weather conditions on crop growth and yield on regional scale (provinces, countries, continents). Therefore, CGMS combines aspects of both weather data processing and collection as well as modelling crop growth and development

Exploring predictive factors in depression treatment:The role of patient characteristics and psychodynamic diagnosis

Dekker, J.J.M. [Promotor]Schoevers, R.A. [Copromotor

Life Expectancy of Daily Newspapers in the Netherlands: The Period 1848 - 1997.

In 1848 freedom of press was written into the Constitution of the Kingdom of the Netherlands. This paper investigates the expected life span of daily newspapers in the Netherlands since then. Life expectancy depends on the cyclical evolution of the number of daily newspapers through time. The life cycle of the competitive newspaper industry in the Netherlands is characterized by a turning period of turmoil during World War II. Models that aim at estimating the expected lifetime of newspaper that do not acknowledge the cyclical characteristics of the industry are most likely misspecified.Economics ;

IT architecture of the MARS crop yield forecasting system

The Crop Growth Monitoring System (CGMS) provides operational services and analysis tools to the Joint Research Centre of the European Commission (JRC) in the area of crop monitoring and crop yield forecast, as part the MARS Crop Yield Forecasting System