Kinetic kd-trees

We propose a simple variant of kd-trees, called rankbased kd-trees, for sets of points in Rd. We show that a rank-based kd-tree, like an ordinary kd-tree, supports range search queries in O(n1-1/d + k) time, where k is the output size. The main advantage of rank-based kd-trees is that they can be efficiently kinetized: the KDS processes O(n2) events in the worst case, assuming that the points follow constantdegree algebraic trajectories, each event can be handled in O(log n) time, and each point is involved in O(1) certificates

Exploring the trade-off between quality and fairness in human partner choice

Partner choice is an important force underpinning cooperation in humans and other animals. Nevertheless, the mechanisms individuals use to evaluate and discriminate among partners who vary across different dimensions are poorly understood. Generally, individuals are expected to prefer partners who are both able and willing to invest in cooperation but how do individuals prioritize the ability over willingness to invest when these characteristics are opposed to one another? We used a modified Dictator Game to tackle this question. Choosers evaluated partners varying in quality (proxied by wealth) and fairness, in conditions when wealth was relatively stable or liable to change. When both partners were equally fair (or unfair), choosers typically preferred the richer partner. Nevertheless, when asked to choose between a rich-stingy and a poor-fair partner, choosers prioritized fairness over wealth—with this preference being particularly pronounced when wealth was unstable. The implications of these findings for real-world partner choice are discussed

Streaming algorithms for line simplification under the Fréchet distance

We study the following variant of the well-known linesimplification problem: we are getting a possibly infinite sequence of points p0, p1, p2, . . . defining a polygonal path, and as we receive the points we wish to maintain a simplification of the path seen so far. We study this problem in a streaming setting, where we only have a limited amount of storage so that we cannot store all the points. We analyze the competitive ratio of our algorithm, allowing resource augmentation: we let our algorithm maintain a simplification with 2k (internal) points, and compare the error of our simplification to the error of the optimal simplification with k points

Kinetic collision detection for balls rolling on a plane

This abstract presents a first step towards kinetic col- lision detection in 3 dimensions. In particular, we design a compact and responsive kinetic data struc- ture (KDS) for detecting collisions between n balls of arbitrary sizes rolling on a plane. The KDS has size O(n log n) and can handle events in O(log n) time. The structure processes O(n2) events in the worst case, assuming that the objects follow low-degree al- gebraic trajectories. The full paper [1] presents ad- ditional results for convex fat 3-dimensional objects that are free-flying in R3

Geodesic spanners for points on a polyhedral terrain

Let S be a set S of n points on a polyhedral terrain T in R3, and let " > 0 be a xed constant. We prove that S admits a (2 + ")-spanner with O(n log n) edges with respect to the geodesic distance. This is the rst spanner with constant spanning ratio and a near-linear number of edges for points on a terrain. On our way to this result, we prove that any set of n weighted points in Rd admits an additively weighted (2 + ")-spanner with O(n) edges; this improves the previously best known bound on the spanning ratio (which was 5 + "), and almost matches the lower bound

Structural and chemical evolution of single-wall carbon nanotubes under atomic and molecular deuterium interaction

The interaction of atomic (D) and molecular (D2) deuterium, as present in a (D + D2) gas mixture, with single-wall carbon nanotubes (SWNTs) has been studied by means of a combination of scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. The SWNT samples were exposed to the gas mixture, produced by thermal dissociation of D2 on a hot W filament, its temperature, TW, being kept at 1020 and 1550 K for a deuterium pressure of 0.6 and 60 Pa, respectively. Prolonged interaction of the low-pressure (D + D2) gas mixture produced at TW = 1020 K leads to a conglomeration of the SWNT bundles into larger diameter ropes of square and triangular cross-section, covered by nano-aggregates of graphite material. Both the coalescence of single SWNTs and a massive reconstruction of bundles of SWNTs into a “coral reef”-like structure were found to occur after prolonged exposure of SWNTs to the high-pressure (D + D2) gas mixture produced at TW = 1550 K. This structure is formed by the encapsulated Fe nanoparticles and deuterocarbon-like species appearing as a result of the deuterium interaction with the SWNT bundles accompanied by partial erosion of the SWNT material. The XPS valence-band spectra disclose electronic features characteristic for a hydrogen-plasma modified multi-wall carbon nanotube (MWNT)-like structure as a result of an intensive (D + D2) induced transformation of the SWNTs into the “coral reef”-like structure

Duurzaamheid in de ogen van de consument; Consumentenonderzoek Duurzaam in retail

Consumentenonderzoek waarin op een kwalitatieve manier onderzocht is hoe mainstream-consumenten duurzaamheid in het algemeen en in retail beleven. Dit rapport verschijnt als onderdeel van Duurzaam in retail. A consumer study involving qualitative research into how mainstream consumers perceive sustainability in general and within the retail sector. This report has been published as part of Duurzaam in retail (Sustainability in the retail sector)