In what follows an upper bound for the probability of erroneous decoding in a coded DHA FH OFDMA system with a noncoherent ML detector under multitone jamming is introduced.

The paper describes a new method of constructing semantic expansions of search requests about the achievements and failures of active systems (organizations, people) for improving the results of Web search. This method is based on the theory of K-representations (knowledge representations), proposed by V.A. Fomichov - a new theory of designing semantic-syntactic analysers of natural language texts with the broad use of formal means for representing input, intermediary, and output data. The method uses an original formal model of a goals base - a knowledge base containing the information about the goals of active systems. The stated approach is implemented with the help of the Web programming language Java: an experimental search system AOS (Aspect Oriented Search) has been developed and tested.

Гибрид двух новых методов, спектральной кластеризации и метод таксономии - применяется для анализа научно-исследовательской деятельности кафедры. Приведенн пример, иллюстрирующий этот метод, который применяется для решения реальных задач.

Cohen et al. developed an O(log n)-approximation algorithm for minimizing the total hub label size (l1 norm). We give O(log n)- approximation algorithms for the problems of minimizing the maximum label (l∞ norm) and minimizing lp and lq norms simultaneously.

The topic of recommender systems is rapidly gaining interest in the user-behaviour modeling research domain. Over the years, various recommender algorithms based on different mathematical models have been introduced in the literature. Researchers interested in proposing a new recommender model or modifying an existing algorithm should take into account a variety of key performance indicators, such as execution time, recall and precision. Till date and to the best of our knowledge, no general cross-validation scheme to evaluate the performance of recommender algorithms has been developed. To fill this gap we propose an extension of conventional cross-validation. Besides splitting the initial data into training and test subsets, we also split the attribute description of the dataset into a hidden and visible part. We then discuss how such a splitting scheme can be applied in practice. Empirical validation is performed on traditional user-based and item-based recommender algorithms which were applied to the MovieLens dataset.

A digraph G = (V,E) with a distinguished set T ⊆ V of terminals is called inner Eulerian if for each v ∈ V − T the numbers of arcs entering and leaving v are equal. By a T-path we mean a simple directed path connecting distinct terminals with all intermediate nodes in V −T. This paper concerns the problem of finding a maximum T-path packing, i.e. a maximum collection of arc-disjoint T-paths. A min-max relation for this problem was established by Lomonosov. The capacitated version was studied by Ibaraki,  Karzanov, and Nagamochi, who came up with a strongly-polynomial algorithm of complexity O(φ(V,E) ・ log T +V 2E) (hereinafter φ(n,m) denotes the complexity of a max-flow computation in a network with n nodes and m arcs). For unit capacities, the latter algorithm takes O(φ(V,E) ・ log T +V E) time, which is unsatisfactory since a max-flow can be found in o(V E) time. For this case, we present an improved method that runs in O(φ(V,E) ・ log T + E log V ) time. Thus plugging in the max-flow algorithm of Dinic, we reduce the overall complexity from O(V E) to O(min(V 2/3E,E3/2) ・ log T).

Concept stability was used in numerous applications for selecting concepts as biclusters of similar objects. However, scalability remains a challenge for computing stability. The best algorithms known so far have algorithmic complexity quadratic in the size of the lattice. In this paper the problem of approximate stability computation is analyzed. An approximate algorithm for computing stability is proposed. Its computational complexity and results of computer experiments in comparing stability index and its approximations are discussed.

We present a new concept of biclique as a tool for preimage attacks, which employs many powerful techniques from differential cryptanalysis of block ciphers and hash functions. The new tool has proved to be widely applicable by inspiring many authors to publish new results of the full versions of AES, KASUMI, IDEA, and Square. In this paper, we show how our concept leads to the first cryptanalysis of the round-reduced Skein hash function, and describe an attack on the SHA-2 hash function with more rounds than before.

An additive spectral method for fuzzy clustering is presented. The method operates on a clustering model which is an extension of the spectral decomposition of a square matrix. The computation proceeds by extracting clusters one by one, which allows us to draw several stoppingrules to the procedure. We experimentally test the performance of our method and show its competitiveness.method and show its competitiveness.

Let G = (V,E) be a digraph with disjoint sets of sources S ⊂ V and sinks T ⊂ V endowed with an S–T flow f : E → Z+. It is a well-known fact that f decomposes into a sum_st(fst) of s–t flows fst between all pairs of sources s ∈ S and sinks t ∈ T . In the usual RAM model, such a decomposition can be found in O(E log V 2 E ) time. The present paper concerns the complexity of this problem in the external memory model (introduced by Aggarwal and Vitter). The internal memory algorithm involves random memory access and thus becomes inefficient. We propose two novel methods. The first one requires O(Sort(E) log V 2 E ) I/Os and the second one takes O(Sort(E) log U) expected I/Os (where U denotes the maximum value of f).