Let T be a d-dimensional toroidal grid of n points. For a given range parameter ω, and a positive integer k ≤ d, we say that two points in T are mutually visible if they differ in at most k coordinates and are a distance at most ω apart, where distance is measured using the `p norm. We obtain a random d-dimensional line-of-sight graph G by placing a node at each point in T independently with so...

A ve-parameter tting formula for the line-of-sight stellar velocity distributions of steady state systems is proposed. It can faithfully reproduce velocity distributions of theoretical models ranging from nearly Gaussian prooles to strongly skewed or mildly double-peaked prooles. In contrast to van der Marel and Franx (1993) and Kuijken and Merriield (1993), the line prooles are required to hav...

The millimeter-wave (mmWave) technology, recently standardized by IEEE 802.11ad, is emerging as an attractive alternative to the traditional 2.4/5GHz wireless systems, promising multi-Gigabit wireless throughput. However, the high attenuation and vulnerability to blockage of 60 GHz links have limited its applications (until recently) to short-range, lineof-sight, static scenarios. On the other ...

Emerging wireless communication systems will be characterized by a tight coupling between communication and positioning. This is particularly apparent in millimeter-wave (mm-wave) communications, where devices use a large number of antennas and the propagation is well described by geometric channel models. For mm-wave communications, initial access, consisting in the beam selection and alignmen...

The error performance of distributed space-time codes used for mobile broadcasting systems consisting of multiple base stations is analysed. The base stations are assumed to operate in a simulcast mode, i.e., they simultaneously transmit the same message using the same carrier frequency. Mobile users within the intersection of the coverage areas thus enjoy a small probability of shadowing and a...

The probability that high-redshift quasars are gravitationally-lensed by intervening galaxies increases rapidly with the cosmological constant, ΩΛ0 (whilst being only weakly dependent on the density parameter, Ωm0), and the low number of lenses observed implies that ΩΛ0 ∼< 0.7 (e.g. Kochanek 1996). One of many uncertainties has been the (small) core radii of elliptical galaxies, which, at least...

I discuss the effect of the formation of a black hole on a (close) binary and show some of the current constraints that the observed properties of black hole X-ray binaries put on the formation of black holes. In particular I discuss the evidence for and against asymmetric kicks imparted on the black hole at formation and find contradicting answers, as there seems to be evidence for kick for in...

Many military simulations and computer entertainment products share a need to model the ability of individual entities (men, tanks, planes, etc.) to see one another and to hide from one another in a 3D virtual environment. The traditional line-of-sight (LOS) visibility model can cause serious problems with hiding behavior. Three alternative visibility models and corresponding algorithms for com...

The present paper develops a novel strategy for the exploration of an unknown environment with a multirobot system. Contrary to most exploration problems, the topographical properties of the space need not be mapped. The algorithm we propose is inspired by methods used for complete coverage of an area, where all free space has to be physically covered by all robots. In the present paper it is r...

While both IR and THz/mmW wireless communications share some attributes such as line-of-sight signaling, their behaviors in response to various weather phenomena such as rain, fog, dust, and air turbulence can be quite different. The performance of mmW/THz and infrared freespace communication links are compared under the same weather conditions.