The multi-robot exploration problem is to explore an unknown graph of size n and depth d with k robots starting from the same node. For known graphs a traversal of all nodes takes at most O(d + n/k) steps. The ratio between the time until cooperating robots explore an unknown graph and the optimal traversal of a known graph is called the competitive exploration time ratio. It is known that for ...

In this paper we present an algorithm to compute the Lyndon array of a string T of length n as a byproduct of the inversion of the Burrows-Wheeler transform of T . Our algorithm runs in linear time using only a stack in addition to the data structures used for Burrows-Wheeler inversion. We compare our algorithm with two other linear-time algorithms for Lyndon array construction and show that co...

This paper proposes a novel watermarking scheme against geometric attacks, combined with the holographic technology and the log-polar transform. In this paper, we first use discrete cosine transform into the original image, then do edge detection for the low frequency part, then do log-polar transform to edge image and make it binarization. We use a key to choose a certain size of the binary im...

We extend the recent sparse Fourier transform algorithm of [1] to the noisy setting, in which a signal of bandwidth N is given as a superposition of k N frequencies and additive noise. We present two such extensions, the second of which exhibits a novel form of error-correction in its frequency estimation not unlike that of the β-encoders in analog-to-digital conversion [2]. The algorithm runs ...

Detecting lines in images using pyramid architecture is the main subject of this paper. The approach is based on the parallel calculation of Hough Transform. A pyramid architecture of size n is a ne-grain architecture with a mesh base of size p n p n processors each holding a single pixel of the image. The pyramid operates in an SIMD mode. Two algorithms for computing the Hough Transform are ex...

We present on O(n log n) greedy algorithm with a worst-case performance ratio > 4 for the unbounded knapsack problem, an O(n log n) greedy algorithm with a worst-case performance ratio of ~ for the subset-sum problem, and an O(n log n) greedy algorithm with a worst-case performance ratio of ~for the partition problem. These greedy algorithms, in the sense of worst-case performance, are better t...

A method for locating underground pipes from a pulse radar image is presented. The method employs the Laplacian of Gaussian filter to extract edges and employs the Hough transform to determine the depth of the pipes. A preliminary experiment showed its ability to detect deeply buried pipes with weak signal echoes. key words: radar image, Hough transform, LoG filter, underground locating