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The problem of creation of quasi-orthogonal signals ensembles with a large number of isomorphic transformations to improve the structural secrecy of asynchronous address radio systems is considered. The chosen subclass of the code sequences ensembles is characterized by a set of options of isomorphic sets creation, the search and enumeration of which is a nontrivial computational problem. Justification...
Minimal Steiner tree problem on graphs is a traditional optimization problem, which has wide- spread use in different application areas. Greedy heuristics for all the people to use the problem are using the shortest path heuristic, and various variants are also used. In this paper, a new heuristic for solving STPG is proposed. The new heuristic defined a novel neighborhood for local search methods...
Spanning subgraph is necessary for the communication in networks. For example, the malfunctioning of one or more nodes in a network in general affects both the global and the local properties of the remaining nodes, because it makes some edges unusable and destroys the connectivity of the system. In this study, we focus on the characters of a network to be fractional-r-factors, fractional (r, k)-extendable...
Summary form only given. A common task in probabilistic modeling is finding the assignment with maximum probability given a model. This is often referred to as the MAP (maximum a-posteriori) problem. Of particular interest is the case of MAP in graphical models, i.e., models where the probability factors into a product over small subsets of variables. For general models, this is an NP-hard problem,...
Protein binding sites are often represented by means of graphs capturing their most important geometrical and physicochemical properties. Searching for structural similarities and identifying functional relationships between them can thus be reduced to matching their corresponding graph descriptors. In this paper, we propose a method for the structural analysis of protein binding sites that makes...
We show that for every fixed k, there is a linear time algorithm that decides whether or not a given graph has a vertex set X of order at most k such that G-X is planar (we call this class of graphs k-apex), and if this is the case, computes a drawing of the graph in the plane after deleting at most k vertices. In fact, in this case, we shall determine the minimum value l ? k such that after deleting...
Cognitive radios must be able to form collaborative wireless network clusters in dynamically changing environments to achieve such desired objectives as interference resilience and low communications overhead. In this work, we explore the affinity propagation (AP) message-passing technique to efficiently group nodes in an ad hoc cognitive radio network (CRN). With the proposed approach, nodes exchange...
We study the inapproximability of Vertex Cover and Independent Set on degree d graphs. We prove that: (1) Vertex Cover is Unique Games-hard to approximate to within a factor 2 - (2 + od(1)) log log d/log d. This exactly matches the algorithmic result of Halperin up to the od(1) term. (2) Independent Set is Unique Games-hard to approximate to within a factor O(d/log2d). This improves the d/logO(1)(d))...
The minimum connected dominating set (MCDS) of a given graph G is the smallest sub-graph of G such that every vertex in G belongs either to the sub-graph or is adjacent to a vertex of the sub-graph. Finding the MCDS in an arbitrary graph is a NP-Hard problem, and several approximation algorithms have been proposed for solving this problem in deterministic graphs, but to the best of our knowledge no...
Hierarchical clustering is a stepwise clustering method usually based on proximity measures between objects or sets of objects from a given data set. The most common proximity measures are distance measures. The derived proximity matrices can be used to build graphs, which provide the basic structure for some clustering methods. We present here a new proximity matrix based on an entropic measure and...
Selecting a small set of nodes called pivots, from all the nodes in a network and maintaining the routing infrastructure to and among each other can reduce routing overhead and excessive broadcast redundancy. In this paper a new problem, called "k-fold cover t- set" (for short, k-fold cover), is proposed: we select a smaller set of nodes than the k-fold dominating set, to act as alternative...
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