Informatica

In this paper we propose and analyze a multilayer perceptron-like model with matrix inputs. We applied the proposed model to the financial time series prediction problem, compared it with the standard multilayer perceptron model, and got fairly good results.

The paper describes the development of the efficient interface sharpening procedure for viscous incompressible flows governed by the Navier–Stokes equations. The moving interface has been captured by a pseudo-concentration method. The solution domain has been discretised by the space-time finite elements, while numerical schemes have been stabilised by the Galerkin least squares method. The dam break problem including breaking waves has been solved in order to validate the performance of the numerical technique. The computed position of the leading edge of water column has been compared with the experimental measurements. The detailed investigation of numerical parameters governing the sharpness of the front and mass conservation has been presented.

The present work is concerned with speech recognition using a small or medium size vocabulary. The possibility to use the English speech recognizer for the recognition of Lithuanian was investigated. Two methods were used to deal with such problems: the expert-driven (knowledge-based) method and the data-driven one. Phonological systems of English and Lithuanian were compared on the basis of the knowledge of phonology, and relations between certain Lithuanian and English phonemes were established. Situations in which correspondences between the phonemes were to be established experimentally (i.e., using the data-driven method) and the English phonemes that best matched the Lithuanian sounds or their combinations (e.g., diphthongs) in such situations were identified. The results obtained were used for creating transcriptions of the Lithuanian names and surnames that were used in recognition experiments. The experiments without transcriptions, with a single transcription and with many transcriptions were carried on. The method that allowed finding a small number of best transcriptions was proposed. The recognition rate achieved was as follows: 84.2% with the vocabulary containing 500 word pairs.

In this paper, we present a novel fine-grained access control system for applications where the information flow is critical; the confidentiality of the data is essential and there are a huge number of users who access different portions of an XML document as in military applications. We combine MAC and RBACK models for XML for use in the mentioned type of applications. In accordance with the peculiarities of the target applications, the access control model is structured in such a way that the implementation can be done efficiently for large number of users. In the system presented, instead of using access control lists, we use a security labeling approach in defining the grant rules. By combining the advantages of role-based and mandatory access control schemes, the access control system presented provides a fine-grained, flexible and effective access for applications where the confidentiality of data is crucial. The system is implemented and tested for correctness. Performance analysis is also given.

This paper examins approaches for translation between English and morphology-rich languages. Experiment with English–Russian and English–Lithuanian revels that “pure” statistical approaches on 10 million word corpus gives unsatisfactory translation. Then, several Web-available linguistic resources are suggested for translation. Syntax parsers, bilingual and semantic dictionaries, bilingual parallel corpus and monolingualWeb-based corpus are integrated in one comprehensive statistical model. Multi-abstraction language representation is used for statistical induction of syntactic and semantic transformation rules called multi-alignment templates. The decodingmodel is described using the feature functions, a log-linear modeling approach and A* search algorithm. An evaluation of this approach is performed on the English–Lithuanian language pair. Presented experimental results demonstrates that the multi-abstraction approach and hybridization of learning methods can improve quality of translation.

This paper presents a novel robust digital image watermarking scheme using subsampling and nonnegative matrix factorization. Firstly, subsampling is used to construct a subimage sequence. Then, based on the column similarity of the subimage sequence, nonnegative matrix factorization (NMF) is applied to decompose the sequence. A Gaussian pseudo-random watermark sequence is embedded in the factorized decomposition coefficients. Because of the high similarity of subimages and meaningful factorization for NMF, the proposed scheme can achieve good robustness, especially to common permutation attacks. Numerical experiment results demonstrate the good performance of the proposed scheme.

A new computational methodology for executing calculations with infinite and infinitesimal quantities is described in this paper. It is based on the principle ‘The part is less than the whole’ introduced by Ancient Greeks and applied to all numbers (finite, infinite, and infinitesimal) and to all sets and processes (finite and infinite). It is shown that it becomes possible to write down finite, infinite, and infinitesimal numbers by a finite number of symbols as particular cases of a unique framework. The new methodology has allowed us to introduce the Infinity Computer working with such numbers (its simulator has already been realized). Examples dealing with divergent series, infinite sets, and limits are given.

A transitive distributed knowledge logic is considered. The considered logic S4nD is obtained from multi-modal logic S4n by adding transitive distributed knowledge operator. For a fragment of this logic loop-check-free sequent calculus is proposed. The considered fragment is such that it can be applied for specification and verification of safety properties of knowledge-based distributed systems. By relying on the constructed loop-check-free sequent calculus a PSPACE procedure to determine a termination of backward derivation in considered fragment of the logic S4nD is presented.

The aim of the given paper is development of a recursive approach for calculating the statistics of decimated realizations of a basic discrete-time signal, obtained by sampling a continuous-time one. The statistics values are calculated without storing decimated realizations in the memory of a computer. In such a case, only all samples of the basic discrete-time signal are required. The summing calculation amount has been significantly reduced here by applying recursive expressions that use, in the current operation, the respective statistic obtained by processing the samples of a previous decimated realization. We prove the corollaries referring to recursive statistics calculation and present here an example. The results of calculation of the total quantity of computer operations for a different amount of decimated signals are also given and compared to that, determined by using the ordinary formulas.