Showing papers on "Adjacency list published in 1980"

Fault tolerance of a class of connecting networks

Abstract: Several proposals have been made for using a class of connecting networks called b-networks in multicomputer systems, such as systems containing large numbers of microprocessors. A b-network is a network of 2 × 2 crossbar switches called b-elements. This paper presents an analysis of the fault tolerance of b-networks intended for multicomputer applications. A fault model is used which allows b-elements to be stuck in either of their two normal states. A new connectivity property called dynamic full access (DFA) is introduced which serves as the criterion for fault tolerance. A b-network is said to have the DFA property if each of its inputs can be connected to any of its outputs in a finite number of passes through the network. A fault is called critical if it destroys the DFA property. Two graph-theoretical characterizations of the critical faults of a b-network are presented. It is shown that there is a one-to-one correspondence between minimal critical faults and the cutsets of the circuit adjacency graphs derived from the b-network. It is further shown that a fault is critical if and only if it is incompatible with all Eulerian circuits associated with the b-network. Some applications of the theory are discussed.

An Approach to Built-Form Connectivity at an Urban Scale: Relationships between Built-Form Connectivity, Adjacency Measures, and Urban Spatial Structure

Abstract: The objective of this paper is to study the relations between connectivity and adjacency measures, developed in previous papers, as functions of the urban spatial structure, by means of multivariate statistical techniques at two levels of resolution and spatial aggregation for the kilometre square cells used to record the town of Reading, England It is shown that of the measures studied one should be discarded as it has no functional relation with the urban spatial structure and the others are structurally interdependent with it It is concluded that, after having validated these measures with the urban spatial structure, they can be used as indices of built-form development

An Approach to Built-Form Connectivity at an Urban Scale: Relationships between Built-Form Connectivity, Adjacency Measures, and Urban Spatial Structure

Abstract: The objective of this paper is to study the relations between connectivity and adjacency measures, developed in previous papers, as functions of the urban spatial structure, by means of multivariate statistical techniques at two levels of resolution and spatial aggregation for the kilometre square cells used to record the town of Reading, England. It is shown that of the measures studied one should be discarded as it has no functional relation with the urban spatial structure and the others are structurally interdependent with it. It is concluded that, after having validated these measures with the urban spatial structure, they can be used as indices of built-form development.

An Image Enhancement Algorithm Based Upon The Photographic Adjacency Effect

Abstract: This paper introduces a non-linear, image dependent, two dimensional filter for enhancing electro-optical images. The filter is termed the Diffusion Model Transformation (DMT) and is based upon the EIKONIX Diffusion Model for the photographic adjacency effect. The paper first discusses the photographic adjacency effect and presents several illustrations of its image enhancement potential. The DMT algorithm is then defined and examples of its application to electro-optical infrared imagery are presented.© (1980) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Pseudographic realizations of an infinitary degree sequence

Abstract: This paper investigates pseudographs with degree sequences which have infinitely many terms greater than 1. Two nonisomorphic pseudographs with the same degree sequence are adjacent if one can be obtained from the other by an elementary operation called switching. With this notion of adjacency we can regard distinct pseudographs with the same degree sequence as the vertices of a graph, called the graph of pseudographic realizations of that sequence. Some results concerning the nature of the components of such graphs of realizations have already been obtained. We add to these results here and, in particular, determine all cases in which the graph has a component which is a path, and all cases in which it has an endvertex.

A computational theory of spatio-temporal aggregation for visual analysis of objects in dynamic environments

Abstract: A theory of spatio-temporal aggregation is introduced as an explanation of what it is possible to compute at an early stage in the visual analysis of objects. Spatio-temporal aggregation is defined as the process of grouping together elements in an image sequence whose motions and positions have consistent interpretations as the retinal projections of a coherent or isolated cluster of 'particles' in the physical world. The information abstracted by spatio-temporal aggregation represents early decisions about which distinct elements belong to the same physical entities or object fragments and estimations of the motions of those fragments relative to the observer. The assumptions of confluence and adjacency are made in order to constrain the infinity of possible interpretations to a computationally more manageable domain of plausible interpretations. It is shown that confluence and adjacency lead to the derivation of specific rules for grouping which permit the appropriate aggregation of rigid and quasi-rigid objects in motion and at rest under a variety of conditions. The theory is reconciled with existing computational theories of vision so as to complement them, and to provide a useful link in the continual abstraction of visual information.