8929657
Drawing Planar Graphs Symmetrically, II: Biconnected Planar Graphs
AbstractSymmetry is one of the most important aesthetic criteria in graph
drawing because it reveals the structure in the graph. This paper
discusses symmetric drawings of biconnected planar graphs. More
specifically, we discuss geometric automorphisms, that is,
automorphisms of a graph G that can be represented as symmetries
of a drawing of G. Finding geometric automorphisms is the first
and most difficult step in constructing symmetric drawings of
graphs. The problem of determining whether a given graph has a
non-trivial geometric automorphism is NP-complete for general
graphs. In this paper we present a linear time algorithm for
finding planar geometric automorphisms of biconnected planar
graphs. A drawing algorithm is also discussed.
653040
The Puzzle Layout Problem
This poster describes an implementation of the puzzle generators and puzzle layouts introduced in [1].
11764310
Symmetric drawings of triconnected planar graphs
Symmetry is one of the most important aesthetic criteria in graph drawing because it reveals structure in the graph. To draw graphs symmetrically, we need two steps. The first step is to find appropriate automorphisms. The second step is to draw the graph to display the automorphisms. Our aim in this paper is to construct maximally symmetric straight-line drawings of triconnected planar graphs in linear time. Previously known algorithms run in quadratic time. We show that an algorithm of Fontet can be used to find an embedding in the plane with the maximum number of symmetries, and present a new algorithm for finding a straight line drawing that achieves that maximum. Both algorithms run in linear time.
1395152
A Group-Theoretic Method for Drawing Graphs Symmetrically
Constructing symmetric drawings of graphs is NP-hard. In this paper, we present a new method for drawing graphs symmetrically based on group theory. More formally, we define a n-geometric automorphism group of a graph that can be displayed as symmetries of a drawing of the graph in n dimensions. Then we present an algorithm to find all 2- and 3-geometric automorphism groups of a graph. We implement the algorithm using Magma [11] and the experimental results shows that our approach is very efficient in practice. We also present a drawing algorithm to display a 2- or 3-geometric automorphism group.
1910054
A neuromorphic model for achromatic and chromatic surface representation of natural images
This study develops a neuromorphic model of human lightness perception that is inspired by how the mammalian visual system is designed for this function. It is known that biological visual representations can adapt to a billion-fold change in luminance. How such a system determines absolute lightness under varying illumination conditions to generate a consistent interpretation of surface lightness remains an unsolved problem. Such a process, called 'anchoring' of lightness, has properties including articulation, insulation, configuration, and area effects. The model quantitatively simulates such psychophysical lightness data, as well as other data such as discounting the illuminant, and lightness constancy and contrast effects. The model retina embodies gain control at retinal photoreceptors, and spatial contrast adaptation at the negative feedback circuit between mechanisms that model the inner segment of photoreceptors and interacting horizontal cells. The model can thereby adjust its sensitivity to input intensities ranging from dim moonlight to dazzling sunlight. A new anchoring mechanism, called the Blurred-Highest-Luminance-As-White rule, helps simulate how surface lightness becomes sensitive to the spatial scale of objects in a scene. The model is also able to process natural color images under variable lighting conditions, and is compared with the popular RETINEX model.
30474248
Crossing Minimization for Symmetries
We consider the problem of drawing a graph with a given symmetry such that the number of edge crossings is minimal. We show that this problem is NP-hard, even if the order of orbits around the rotation center or along the reflection axis is fixed. Nevertheless, there is a linear time algorithm to test planarity and to construct a planar embedding if possible. Finally, we devise an O (m log m) algorithm for computing a crossing minimal drawing if inter-orbit edges may not cross orbits, showing in particular that intra-orbit edges do not contribute to the NP-hardness of the crossing minimization problem for symmetries. From this result, we can derive an O (m log m) crossing minimization algorithm for symmetries with an orbit graph that is a path.
3107205
Crossing Minimization for Symmetries
AbstractWe consider the problem of drawing a graph with a given symmetry
 such that the number of edge crossings is minimal. We show that this
 problem is NP-hard, even if the order of orbits around the rotation
 center or along the reflection axis is fixed.
 We devise an O(m log m) algorithm
 for computing a crossing minimal drawing if inter-orbit edges may
 not cross orbits, showing in particular that intra-orbit edges do
 not contribute to the NP-hardness of the crossing minimization
 problem for symmetries.
20165974
An intelligent image retrieval system using XML
With the rapid development of Internet technology, the number of Internet users and the amount of multimedia information on the Internet is ever increasing. Recently, the Web sites, such as e-business sites and shopping mall sites, deal with lots of image information. As a result, it is required to support content-based image retrieval efficiently on such image data. This paper proposes an intelligent image retrieval system, which adopts XML technology. To support object-based content retrieval on product catalog images containing multiple objects, we describe a multilevel metadata structure representing the local features, global features, and semantics of image data. To enable semantic-based and content-based retrieval on such image data, we design an XML-schema for the proposed metadata. We also describe how to automatically transform the retrieval results into the forms suitable for the various user environments, such as Web browser or mobile browser, using XSLT. The proposed scheme can be utilized to enable efficient image metadata sharing between systems, and it will contribute in improving the retrieval correctness and the user's satisfaction on content-based e-catalog image retrieval.
4639514
Group Hierarchies with Constrained User Assignment in Linux
In this paper we investigate one aspect of RBAC administration concerning assignment of users to roles. A user-role assignment model can also be used for managing user-group assignment. We overview a constrained user-group assignment model and describe its implementation in the Linux system. Rather than set user and file rights individually for each and every user, the administrator can give rights to various groups, then place users within those groups in Linux. Each user within a group inherits the rights associated with that group. We describe an experiment to extend the Linux group mechanism to include group hierarchies and decentralized user-group assignment can be implemented by means of setgid programs.