Many animal species, including some social hymenoptera, use the visual system for navigation. Although the insect compound eyes have been well studied, less is known about the second visual system in some insects, the ocelli. Here we demonstrate navigational functions of the ocelli in the visually guided Australian desert ant Melophorus bagoti. These ants are known to rely on both visual landma...

Path-consistency algorithms, which are polynomial for discrete problems, are exponential when applied to problems involving quantitative temporal information. The source of complexity stems from specifying relationships between pairs of time points as disjunction of intervals. We propose a polynomial algorithm, called ULT, that approximates path-consistency in Temporal Constraint Satisfaction P...

Path-consistency algorithms, which are polynomial for discrete problems, are exponential when applied to problems involving quantitative temporal information. The source of complexity stems from specifying relationships between pairs of time points as disjunction of intervals. We propose a polynomial algorithm, called ULT, that approximates path-consistency in Temporal Constraint Satisfaction P...

Ubiquitous sensing devices frequently disseminate data among them. The use of a distributed event-based system that decouples publishers from subscribers arises as an ideal candidate to implement the dissemination process. In this paper, we present a network architecture that merges the network and overlay layers of typical structured event-based systems. Directional random walks are used for t...

We propose and demonstrate a single-fiber bi-directional WDM self-healing ring network with simple bidirectional OADM. By employing our proposed alternate-path switching scheme, the bi-directional traffic can be restored promptly under single fiber failure. Introduction Bi-directional wavelength division multiplexing (WDM) self-healing ring (SHR) network [1-2] is an attractive and cost-effectiv...

A directed path whose edges are assigned labels “up”, “down”, “right”, or “left” is called four-directional, and three-directional if at most three out of the four labels are used. A direction-consistent embedding of an n-vertex threeor four-directional path P on a set S of n points in the plane is a straight-line drawing of P where each vertex of P is mapped to a distinct point of S and every ...

SONET technology has made high-speed self-healing ring (SHR) architectures practical and economical for use in intra-LATA telecommunication networks. This paper reviews a class of SONET SHR architectures and their control schemes. The SHR architectures can be divided into two basic classes: bi-directional SHRs (B-SHRs) and uni-directional SHRs (U-SHRs). Bidirectional SHRs using four fibers and ...

Classes of coordinate-invariant omnibus goodness-of-fit tests on compact Riemannian manifolds are proposed. The tests are based on Giné's Sobolev tests of uniformity. A condition for consistency is given. The tests are illustrated by an example on the rotation group SO(3). 1. Introduction. Although many tests of goodness of fit are available for distributions on the circle, comparatively little...

Insects typically use celestial sources of directional information for path integration, and terrestrial panoramic information for view-based navigation. Here we set celestial and terrestrial sources of directional information in conflict for homing desert ants (Melophorus bagoti). In the first experiment, ants learned to navigate out of a round experimental arena with a distinctive artificial ...

Query languages for object bases became enriched by generalized path expressions that allow for attribute and path variables. Optimizing queries containing generalized path expressions attracted some interest. However, many interesting queries require still a full scan over the whole object base. This unbearable situation can be remedied best by utilizing index structures. However, traditional ...