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Image Sequence Processing For Target Estimation In Forward-Looking Infrared Imagery

This paper presents a methodology for estimating the silhouette of a target from a time sequence of forward-looking infrared (FLIR) imagery recorded at video rates. The major problems associated with this type of imagery are noise and frame-to-frame misregistration. We achieve registration and noise smoothing by a combination of spatial and temporal processing. Edge-preserving smoothing is applied to individual frames prior to gray level thresholding. A new algorithm for finding the optimum threshold is presented. The resulting sequence of binary image frames is registered by cross-correlating the 1-D x and y projections of each frame. The computationally efficient 1 -D registration technique is just as accurate as a much slower 2-D correlation method. Temporal smoothing is realized by using a binary median filter to process frame sequences. We show that binary temporal median filtering is comparable in performance with gray level median processing followed by thresholding. Our target estimation approach is applicable in situations in which a single target exists against a background of relatively uncorrelated noise.

Matching is as easy as matrix inversion

We present a new algorithm for finding a maximum matching in a general graph. The special feature of our algorithm is that its only computationally non-trivial step is the inversion of a single integer matrix. Since this step can be parallelized, we get a simple parallel (RNC 2) algorithm. At the heart of our algorithm lies a probabilistic lemma, the isolating lemma. We show other applications of this lemma to parallel computation and randomized reductions.

An Efficient Parallel Biconnectivity Algorithm

In this paper we propose a new algorithm for finding the blocks (biconnected components) of an undirected graph. A serial implementation runs in $O(n + m)$ time and space on a graph of n vertices and m edges. A parallel implementation runs in $O(\log n)$ time and $O(n + m)$ space using $O(n + m)$ processors on a concurrent-read, concurrent-write parallel RAM. An alternative implementation runs in $O(n^2 /p)$ time and $O(n^2 )$ space using any number $p \leqq n^2 /\log ^2 n$ of processors, on a concurrent-read, exclusive-write parallel RAM. The last algorithm has optimal speedup, assuming an adjacency matrix representation of the input. A general algorithmic technique that simplifies and improves computation of various functions on trees is introduced. This technique typically requires $O(\log n)$ time using processors and $O(n)$ space on an exclusive-read exclusive-write parallel RAM.

Technical Note—Determining All Optimal and Near-Optimal Solutions when Solving Shortest Path Problems by Dynamic Programming

This paper presents a new algorithm for finding all solutions with objective function values in the neighborhood of the optimum for certain dynamic programming models, including shortest path problems. The new algorithm combines the depth-first search with stacking techniques of theoretical computer science and principles from dynamic programming to modify the usual backtracking routine and list all near-optimal policies. The resulting procedure is the first practical algorithm for a variety of large problems that are of interest.

A new algorithm for finding the shortest path between a specified pair of nodes in a graph of nonnegative arcs

This paper presents a new algorithm for finding the shortest path between a specified pair of nodes in a directed nonnegatively weighted graph. The average number of operations of this algorithm is competitive with that of the best existing algorithm presented by Dijkstra.

Finding the convex hull of a simple polygon

We describe a new algorithm for finding the convex hull of any simple polygon specified by a sequence of m vertices. An earlier convex hull finder of ours is limited to polygons which remain simple (i.e., nonselfintersecting) when locally non-convex vertices are removed. In this paper we amend our earlier algorithm so that it finds with complexity O( m) the convex hull of any simple polygon, while retaining much of the simplicity of the earlier algorithm.

A procedure for finding the nucleolus of a cooperativen person game

The nucleolus is a central concept of solution in the theory of cooperativen person games with side payments; it has been introduced and studied by Schmeidler [1969] and several methods for finding the nucleolus have been proposed byKopelowitz [1967],Bruyneel [1979],Stearns [1968] andJustman [1977], respectively. The aim of the present paper is that of giving a new algorithm for finding the nucleolus and to discuss the relationship of this algorithm with those given by Kopelowitz and Bruyneel. The algorithm is based upon the concept of minimal balanced set of a finite set; this last concept has been introduced for other purposes byShapley [1967]. The relationship between the nucleolus and the balanced sets has been studied byKohlberg [1971], where it has been shown that the so-called coalition array of an imputation is the coalition array of the nucleolus iff some parts of it are balanced sets. Our algorithm computes such a coalition array by finding a sequence of minimal balanced sets. Any element of the sequence can be found be solving a LP problem, then the nucleolus is easily found from the coalition array. The algorithm is in some sense a dual of the Kopelowitz‘ algorithm. It clarifies completely the relationship between the nucleolus and the minimal balanced sets, that allowed the statement of the Bruyneel's algorithm; moreover, our algorithm doesn't assume the knowledge of the list of weight vectors associated to the set of minimal balanced sets, but constructs only the part of the list needed for finding the nucleolus.

An O(V 5/3 E 2/3) algorithm for the maximal flow problem

A new algorithm for finding a maximal flow in a given network is presented. The algorithm runs in time O(V 5/3 E 2/3), where V and E are the number of the vertices and edges in the network.

A new algorithm for finding the peptide chain turns in a globular protein

An algorithm is presented to identify peptide chain turns from X-ray-elucidated co-ordinate data. Chain turns are those regions in a globular protein where the backbone is folded back upon itself. The concept of a turn is important both because turns constitute recognizable structural units in proteins and because turns are situated at the solvent-accessible surface of the molecule. Current algorithms for turn identification are highly operational in character, often finding false turns and omitting actual ones. The algorithm presented here uses only the C-alpha co-ordinates for every residue in the protein. No other information of any kind is required, and notions about hydrogen bonding at these loci are irrelevant to the geometric nature of the argument. In this sense, the algorithm provides an objective criterion for the recognition of turns as strictly structural components in proteins. The algorithm is used to find the turns in a test set of proteins. Results of this application are in excellent agreement with visual turn identification from physical models.

Computational experiences with some transitive closure algorithms

The paper contains results of computational experiences with the following algorithms for finding the transitive closure of a digraph: (i) Warshall's algorithm [17], (ii) Purdom's algorithm [13], (iii) the modification of Yen's algorithm [14], and (iv) the new algorithms for finding the transitive closure [3, 4]. The tested digraphs were generated at random. The enclosed references contain all papers known to the authors concerning transitive closure algorithms.

A New Algorithm for Finding All Shortest Paths in a Graph of Positive Arcs in Average Time $O(n^2 \log ^2 n)$

We present a new algorithm for finding the shortest path between each pair of nodes in a directed nonnegatively weighted graph. Our algorithm has average running time $O(n^2 \log ^2 n)$ where the graph has n nodes in contrast to previous algorithms in the literature, all of whose average running times are $O(n^3 )$ for this problem.

A sorting problem and its complexity

A technique for proving min-max norms of sorting algorithms is given. One new algorithm for finding the minimum and maximum elements of a set with fewest comparisons is proved optimal with this technique.

Generation of trees, cotrees and 2-trees of a linear graph

A new algorithm for finding all trees, cotrees and 2-trees in a connected linear graph is given. The procedure will not generate any duplication, redundancies or cancellation of terms. The method given is based only on the definition of tree, so that no complexity arises. Further, it is shown that, if a certain condition is satisfied by the graph, the 2-trees can be obtained directly from the trees that have been generated. An illustrative example on the algorithm is also given.

A new algorithm for factoring polynomials

A new algorithm for finding the roots of polynomials is presented. The method is based upon an accurate first approximation to a root which is then used to initiate an iterative solution. The method is reliable, rapid, has a high order of convergence, and excellent convergence in the large.