Reconfiguration of 3D Crystalline Robots Using O(log n) Parallel Moves

We consider the theoretical model of Crystalline robots, which have been introduced and prototyped by the robotics community. These robots consist of independently manipulable unit-square atoms that can extend/contract arms on each side and attach/detach from neighbors. These operations suffice to reconfigure between any two given (connected) shapes. The worst-case number of sequential moves required to transform one connected configuration to another is known to be Theta(n). However, in principle, atoms can all move simultaneously. We develop a parallel algorithm for reconfiguration that runs in only O(log n) parallel steps, although the total number of operations increases slightly to Theta(nlogn). The result is the first (theoretically) almost-instantaneous universally reconfigurable robot built from simple units.Comment: 21 pages, 10 figure

Segmenting trajectories: A framework and algorithms using spatiotemporal criteria

In this paper we address the problem of segmenting a trajectory based on spatiotemporal criteria. We require that each segment is homogeneous in the sense that a set of spatiotemporal criteria are fulfilled. We define different such criteria including location heading speed velocity curvature sinuosity curviness and shape. We present an algorithmic framework that allows us to segment any trajectory into a minimum number of segments under any of these criteria or any combination of these criteria. In this framework a segmentation can generally be computed in O(n log n) time where n is the number of edges of the trajectory to be segmented. We also discuss the robustness of our approach

Cost-effectiveness of pregabalin versus venlafaxine in the treatment of generalized anxiety disorder: findings from a Spanish perspective

The objective of the present study was to describe a new model of the cost-effectiveness of treatment of generalized anxiety disorder (GAD) and its application to a comparison of pregabalin versus venlafaxine extended-release (XR) from a Spanish healthcare perspective. Microsimulation techniques, including Hamilton Anxiety Scale (HAM-A) score, number of weeks with minimal or no anxiety (HAM-A ≤ 9), and quality-adjusted life-years (QALYs), were used to predict treatment outcomes for patients with moderate-to-severe GAD who would be treated with pregabalin vs venlafaxine XR. Expected levels of healthcare utilization and unit cost of care are derived from Spanish published sources. We express cost-effectiveness alternatively in terms of incremental cost per additional week with minimal or no anxiety, and incremental cost per QALY gained [in 2007 Euros (€)]. Considering costs of drug treatment only, the incremental cost [mean (95% confidence interval)] of pregabalin (vs venlafaxine XR) would be €96 (€86, €107) per additional week with minimal or no anxiety, and €32,832 (€29,656, €36,308) per QALY gained. When other medical care costs are considered, cost-effectiveness ratios decline to €70 (€61, €80) per additional week with no or minimal anxiety, and €23,909 (€20,820, €27,006) per QALY gained. We conclude that, using a new microsimulation model of the treatment of GAD, pregabalin appears to be cost-effective vs venlafaxine XR in a Spanish healthcare setting

Optimizacion geometrica y aplicaciones en visibilidad

Centro de Informacion y Documentacion Cientifica (CINDOC). C/Joaquin Costa, 22. 28002 Madrid. SPAIN / CINDOC - Centro de Informaciòn y Documentaciòn CientìficaSIGLEESSpai

Small Convex Quadrangulations of Point Sets

In this paper, we give upper and lower bounds on the number of Steiner points required to construct a strictly convex quadrilateral mesh for a planar point set. In particular, we show that 3b 2 c internal Steiner points are always sucient for a convex quadrangulation of n points in the plane. Furthermore, for any given n 4, there are point sets for which d 2 e 1 Steiner points are necessary for a convex quadrangulation

Incidence Angle Constrained Visibility

We present the first part of a study on what we call quality pictures, where we introduce a quality parameter ff that indicates the minimum incidence angle allowed between the vision direction and a seen surface. We solve here some combinatorial and algorithmic problems about both external and internal quality pictures of polygons. 1 Introduction Since 1973, when V. Klee proposed the problem of determining the minimum number of points (guards or cameras) that would always suffice to see any n-polygon, many variations of this problem have been studied [20], [22]. Various studies have considered restricting the class of polygons to be guarded (orthogonal, etc.), new kinds of guards have been introduced (edgeguards, mobile guards,...) and even watchman routes have been studied. Traditionally, it is assumed that guards can see in any direction. If we imagine cameras, instead of guards, this would imply a 360 ffi field of aperture. More recently, more realistic approaches have been propo..