Showing papers on "Adjacency list published in 1995"

Spectral Partitioning: The More Eigenvectors, The Better

Abstract: A spectral partitioning method uses the eigenvectors of a graph's adjacency or Laplacian matrix to construct a geometric representation (e.g., a linear ordering) which is then heuristically partitioned. We map each graph vertex to a vector in d-dimensional space, where d is the number of eigenvectors, such that these vectors constitute an instance of the vector partitioning problem. When all the eigenvectors are used, graph partitioning exactly reduces to vector partitioning. This result motivates a simple ordering heuristic that can be used to yield high-quality 2-way and multi-way partitionings. Our experiments suggest the vector partitioning perspective opens the door to new and effective heuristics.

Edge adjacency relationships and a novel topological index related to molecular volume

Abstract: published in Advance ACS Absrracfs, June 15, 1994. where v,, is the index of refraction and W t h e molar volume. 0095-2338/95/1635-0031$09.00/0

Quasi-transitive digraphs

Abstract: A digraph is quasi-transitive if there is a complete adjacency between the inset and the outset of each vertex. Quasi-transitive digraphs are interseting because of their relation to comparability graphs. Specifically, a graph can be oriented as a quasi-transitive digraph if and only if it is a comparability graph. Quasi-transitive digraphs are also of interest as they share many nice properties of tournaments. Indeed, we show that every strongly connected quasi-transitive digraphs D on at least four vertices has two vertices v1 and v2 such that D – vi is strongly connected for i = 1, 2. A result of tournaments on the existence of a pair of arc-disjoint in- and out-branchings rooted at the same vertex can also be extended to quasi-transitive digraphs. However, some properties of tournaments, like hamiltonicity, cannot be extended directly to quasi-transitive digraphs. Therefore we characterize those quasi-transitive digraphs which have a hamiltonian cycle, respectively a hamiltonian path. We show the existence of highly connected quasi-transitive digraphs D with a factor (a collection of disjoint cycles covering the vertex set of D), which have a cycle of every length 3 ≦ k ≦ |V(D)| − 1 through every vertex and yet they are not hamiltonian. Finally we characterize pancyclic and vertex pancyclic quasi-transitive digraphs. © 1995, John Wiley & Sons, Inc.

Enhanced adjacency detection protocol for wireless applications

Abstract: An Adjacency Detection Protocol (ADP) whereby a node in a wireless network may collect information about its neighbors. The collected information enables the establishment of link layer connectivity between a node and its neighbors and also is useful for translating network layer addresses into link addresses. The collected information finds further use in preventing medium contention among adjacent nodes and in handling collisions.

On representation and matching of multi-coloured objects

Abstract: A new representation for objects with multiple colours-the colour adjacency graph (CAG)-is proposed. Each node of the CAG represents a single chromatic component of the image defined as a set of pixels forming a unimodal cluster in the chromatic scattergram. Edges encode information about adjacency of colour components and their reflectance ratio. The CAG is related to both the histogram and region adjacency graph representations. It is shown to be preserving and combining the best features of these two approaches while avoiding their drawbacks. The proposed approach is tested on a range of difficult object recognition and localisation problems involving complex imagery of non-rigid 3D objects under varied viewing conditions with excellent results. >

Edge adjacency relationships in molecular graphs containing heteroatoms: a new topological index related to molar volume

Abstract: Adjacency between edges in molecular graphs containing heteroatoms is considered by using weights in the nondiagonal entries of the edge adjacency matrix. Values of kc-x parameters used in HMO calculation for molecules containing heteroatoms are used as edges weights. One index is derived using the RandiCtype graph theoretical invariant. This index is well correlated ( r > 0.99) with the molar volume of 112 aliphatic organic compounds, including aldehydes, ketones, ethers, thioethers, tertiary amines, and alkyl halides. A parametrization methods is proposed in order to obtain the values of kc-x parameters, based on correlation found between the proposed index and molar volumes.

Measuring the efficacy of adjacency constraint structure in forest planning models

Abstract: This paper examines various structural representations of adjacency conditions in forest planning problems. It will be shown that alternative representations can rival traditional approaches, which...

Graph theoretic heuristics for unequal-sized facility layout problems

Abstract: We consider the unequal-sized facility layout problem with the objective of minimizing total transportation distance. The total transportation distance is defined as the sum of products of flow amounts and rectilinear distances between facilities, where flow amount represents the number of trips per time period between facilities. In the layout problem, it is assumed that shapes of facilities are not fixed and that there is no empty space between facilities in the layout. We propose new graph theoretic heuristics for the problem. In the heuristics, an initial layout is obtained by constructing a planar adjacency graph and then the solution is improved by changing the adjacency graph (not the physical layout). Therefore, these heuristics do not need an initial layout in advance, and sizes and locations of facilities do not have to be considered in the improvement procedure. Computational results showed that the proposed algorithms gave better solutions than those from CRAFT, which is one of the most popular algorithms for unequal-sized facility layout problems.

Sliceable Floorplanning by Graph Dualization

Abstract: Previous algorithms on rectangular dual graph floorplanning generate general floorplans which include the class of nonsliceable floorplans. We examine the framework of generating sliceable floorplans using the rectangular dual graph approach and present an algorithm that generates a sliceable floorplan if the input graph satisfies certain sufficient conditions. For general input, the algorithm is still able to generate sliceable floorplans by introducing pseudomodules where the areas occupied by the pseudomodules are used for wiring. For an $n$-vertex adjacency graph, the algorithm generates a sliceable floorplan in $O(n \log n + hn)$ time where $h$ is the height of the sliceable floorplan tree.

Polymorphic grouping for image segmentation

Abstract: The paper describes a new approach to image segmentation. It accepts the inherent deficiencies occuring when extracting low-level features and when dealing with the complexity of real scenes. Image segmentation therefore is understood as deriving a rich symbolic description useful for tasks such as stereo or object recognition in outdoor scenes. The approach is based on a polymorphic scheme for simultaneously extracting points, lines and segments in a topologically consistent manner, together with their mutual relations derived from the feature adjacency graph (FAG) thereby performing several grouping steps which gradually use more and more specific domain knowledge to achieve an optimal image description. The heart of the approach is (1) a detailed analysis of the FAG and (2) a robust estimation for validating the found geometric hypotheses. The analysis of the FAG, derived from the exoskeleton of the features, allows to detect inconsistencies of the extracted features with the ideal image model, a cell-complex. The FAG is used for finding hypotheses about incidence relations and geometric hypotheses, such as collinearity or parallelity, also between non-neighbored points and lines. The M-type robust estimation is used for simultaneously eliminating wrong hypotheses on geometric relationships. It uses a new argument for the weighting function. >

Resource placement with multiple adjacency constraints in k-ary n-cubes

Abstract: The problem of placing resources in a k-ary n-cube (k>2) is considered in this paper. For a given j/spl ges/1, resources are placed such that each nonresource node is adjacent to j resource nodes. We first prove that perfect j-adjacency placements are impossible in k-ary n-cubes if n >

Segmenting internal structures in 3D MR images of the brain by Markovian relaxation on a watershed based adjacency graph

Abstract: The authors present a fast stochastic method aiming at segmenting cerebral internal structures in 3D magnetic resonance images. An original method introducing context permits the authors to obtain reliable radiometric characteristics even for hardly discriminable brain structures. Segmentation is formulated as the labeling of a region adjacency graph. The graph is constructed by an extension to 3D of the watershed algorithm and the labeling is performed using a Markovian relaxation process. This leads to consistent results with a very low computational burden.

The Star-Topology: a topology for image analysis

Abstract: Our previous works in image analysis dealing with image representations by means of adjacency or boundary graphs, led us to the need for a coherent representation model. In fact, classical approaches to this problem seem to be unsuffcient or even uncoherent; for example they are unclear with the well-known connectivity paradox or with the border description of regions. Diierent works like those of Kovalevsky, Herman and Malandain pointed out the advantages of cellular complex based topologies [Kovalevsky89, Herman90, Malandain93]. But no one of them suggested a formalism that can be applied to any type of image. In this work we propose a topological representation for any type of image, colour or grey-level of whatever dimension. It is based on convex complexes, and looks closely at the elements realizing the connectivity within complexes and later within regions. Futhermore it remains coherent with pixel and voxel only based representations. An important feature is still maintaining a direct correspondance with the classical IR n topology. Finally, we suggest a characterization of regions, their borders and boundaries which is useful as a basic tool for segmentation.

A graph-based expert system approach to geometric feature recognition

Abstract: Geometric feature recognition is a crucial task in the development of concurrent engineering software. This paper presents a new methodology for geometric feature recognition which combines the advantages of face-edge adjacency graphs and expert systems. The methodology uses several new concepts such as enhanced winged edge data structure (EWEDS) and multi-attributed adjacency graphs (MAAG). The object model is presented as a set of facts. The rules for the recognition of each feature are derived from the corresponding feature-MAAG. This simplifies the process of writing the rules while enabling the inclusion of new features into the rule base as they are encountered.

Region correspondence by inexact attributed planar graph matching

Abstract: An efficient graph matching approach is proposed for finding region correspondence between two images of the same scene but taken from different viewpoints. Regions and their relations in an image are represented with region adjacency graph (RAG), which is a kind of attributed planar graph. The problem to find an optimal region correspondence, which matches the regions in two images with maximal similarity in region features and region relations, is formulated into the problem to find the optimal inexact matching between two RAGs. The properties specific to planar graph and that of the region adjacency relations are utilized to invent an efficient algorithm to solve the problem. Experimental results on various kinds of images show the effectiveness of the method. >

On Skeletons, Diameters and Volumes of Metric Polyhedra

Abstract: We survey and present new geometric and combinatorial properties, of some polyhedra with application in combinatorial optimization, for example, the max-cut and multicommodity flow problems. Namely we consider the volume, symmetry group, facets, vertices, face lattice, diameter, adjacency and incidence relations and connectivity of the metric polytope and its relatives. In particular, using its large symmetry group, we completely describe all the 13 orbits which form the 275 840 vertices of the 21-dimensional metric polytope on 7 nodes and their incidence and adjacency relations. The edge connectivity, the i-skeletons and a lifting procedure valid for a large class of vertices of the metric polytope are also given. Finally, we present an ordering of the facets of a polytope, based on their adjacency relations, for the enumeration of its vertices by the double description method.

Four directional adjacency graphs (FDAG) and their application in locating fields in forms

Abstract: A new non-hierarchical spatial data structure named four directional adjacency graphs (FDAG) is proposed In the FDAG vertical and horizontal neighborhood relationship between rectangles is well represented so that structural information can be easily extracted An application for structural analysis of forms is given, where experiments are conducted with positive results

A new method for optimization of allocation and scheduling in real time applications

Abstract: Performance improvements achievable through parallel processing are useful in real time (RT) environments. The paper describes a method to map (i.e. allocate and schedule) a program with some RT constraints into a parallel system. We formulate the mapping problem as a minimization problem, defining a new cost function whose minimization leads to the optimal mapping of the program into the parallel system. The searching space over which the minimization must be carried out is defined; this space encloses all the feasible allocation and scheduling modalities for the program in the parallel system. The minimization is carried out through a simulated annealing algorithm, so we define an adjacency criterion on the searching space. Some examples illustrating the capabilities of the proposed method are presented.

Vehicle routing problem using genetic algorithms based on adjacency relations

Abstract: In the vehicle routing problem, the traditional crossover operators for genetic algorithms (GAs) could fail to produce legal tours We propose a new crossover operator considering adjacency relations, and compare the new GA with the GA using the partially matched crossover or a branch-and-bound method Some experiments are performed on digital road maps The proposed GA finds optimum solutions effectively

A 3D Molecular Surface Representation Supporting Neighborhood Queries

Abstract: Applications in molecular biology more and more require geometric data management along with physicochemical data handling. Thus, 3D structures and surfaces of molecules become basic objects in molecular databases. We propose the neighborhood query on graphs such as molecular surfaces as a fundamental query class concerning topological information on patch adjacency. Furthermore, we suggest a patch-based data structure, called the TriEdge structure, first, to efficiently support neighborhood query processing, and second, to save space in comparison to common 2D subdivision data structures such as the quad-edge structure or the doubly-connected edge list. In analogy to the quad-edge structure, the TriEdge structure has an algebraic interface and is implemented via complex pointers. However, we achieve a reduction of the space requirement by a factor of four. Finally, we investigate the time performance of our prototype which is based on an object-oriented database management system.

VLSI floorplan generation and area optimization using AND-OR graph search

Abstract: Floorplan design based on rectangular dualization is considered in two phases. First, given the adjacency graph and sets of aspect ratios of the blocks, a topology is generated which is likely to yield a minimum-area floorplan during the second phase of optimal sizing. Since the problem of finding such topology seems to be intractable, a heuristic search method using AND-OR graphs is employed in the top-down first phase. Novel heuristic estimates are used to reduce the search effort. For slicing topologies, a bottom-up polynomial-time algorithm is used to solve the second phase. Moreover, the first phase is able to report inherently nonslicible floorplans. The proposed method outperforms the existing techniques, as evident from the experimental results.

Neural network approach to traveling salesman problem based on hierarchical city adjacency

Abstract: A neural network approach based on city adjacency has been proposed in order to solve the traveling salesman problems. This method, in which a novel energy function is used for TSPs, produces frequently several traveling closed subtours. To cope with this problem, the authors propose a method to make a traveling tour without any closed subtours, where hierarchical city adjacency is considered. It is easy to apply this technique recursively. Therefore, this approach is applicable to larger scale problems.

Parsing Visual Languages with Constraint Multiset Grammars

Abstract: Visual languages, that is two dimensional languages, such as electric circuit diagrams, musical notation, structural-chemical formulae, or mathematical equations have two main differences to one-dimensional text languages. The first is that the basic structure for organizing text, the sequence, is not relevant for two-dimensional input. Although, one might sequence input gestures according to the order in which they were entered, this seems too restrictive there is no one natural order in which people draw a complex diagram. The second is that in text the only relationship between tokens is adjacency, whereas in a diagram the possible relationships are much richer and include geometric relationships such as containment and adjacency. For these reasons we have introduced a new formalism, constraint multiset grammars, (CMGs) [7, 10] which gives a general, high-level framework for the definition of visual languages. Productions in a constraint multiset grammar have the form

A Fast State Assignment Procedure for Large FSMs

Abstract: This paper addresses the problem of state assignment for large Finite State Machines (FSM). This is an important problem in the high performance digital system design where added functionality often comes at the expense of a larger (and slower) FSM to control the system. We present a new method to solve the graph embedding problem which is the main step in the state assignment process. The basic idea is to place the state adjacency graph in a two-dimensional grid while minimizing the total wire length. The grid is then mapped into an n-dimensional hypercube while nearly preserving the adjacency relations that is with dilation at most 2. Experimental results are presented and compared with those of NOVA.

Routing in modular fault-tolerant multiprocessor systems

Abstract: In this paper, we consider a class of modular multiprocessor architectures in which spares are added to each module to cover for faulty nodes within that module, thus forming a fault-tolerant basic block (FTBB). In contrast to reconfiguration techniques that preserve the physical adjacency between active nodes in the system, our goal is to preserve the logical adjacency between active nodes by means of a routing algorithm which delivers messages successfully to their destinations. We introduce two-phase routing strategies that route messages first to their destination FTBB, and then to the destination nodes within the destination FTBB. Such a strategy may be applied to a variety of architectures including binary hypercubes and three-dimensional tori. In the presence of f faults in hypercubes and tori, we show that the worst case length of the message route is min {/spl sigma/+f, (K+1)/spl sigma/}+c where /spl sigma/ is the shortest path in the absence of faults, K is the number of spare nodes in an FTBB, and c is a small constant. The average routing overhead is much lower than the worst case overhead.

Heuristics for a new model of facility layout

Abstract: We define a new model for facility layout and present some heuristics for its solution. The model presents a more realistic representation of the problem than previous ones in that facilities which are nonadjacent yet “close” to each other are compensated in the determination of the optimal adjacency subgraph. Empirical results comparing the heuristics with the method of Leung [11] are also reported.