Informatica

The paper considers moving locally predefined (MLP) finite element remeshing technique for deep penetration of the rigid cone into homogeneous and porous medium. Remeshing presents a computational tool implemented in the form of postprocessor type software compatible with standard FEM codes. It involves a transfer operation combining both the moving least square method based on stress patch recovery and the interpolation method for transfer of state variables. The developed MLP remeshing is able to overcome numerical difficulties occurring due to large distortions of the Lagrangian mesh and contact sliding and capture steady‐state behavior. It shows good performance in modeling of cone penetration into elasto‐plastic homogeneous and porous media reaching several diameters of the cone.

In this paper, the main measure, an amount of information, of the information theory is analyzed and corrected. The three conceptions of the theory on the microstate, dissipation pathways, and self‐organization levels with a tight connection to the statistical physics are discussed. The concepts of restricted information were introduced as well as the proof of uniqueness of the entropy function, when the probabilities are rational numbers, is presented.

The development of Lithuanian HMM/ANN speech recognition system, which combines artificial neural networks (ANNs) and hidden Markov models (HMMs), is described in this paper. A hybrid HMM/ANN architecture was applied in the system. In this architecture, a fully connected three‐layer neural network (a multi‐layer perceptron) is trained by conventional stochastic back‐propagation algorithm to estimate the probability of 115 context‐independent phonetic categories and during recognition it is used as a state output probability estimator. The hybrid HMM/ANN speech recognition system based on Mel Frequency Cepstral Coefficients (MFCC) was developed using CSLU Toolkit. The system was tested on the VDU isolated‐word Lithuanian speech corpus and evaluated on a speaker‐independent ∼750 distinct isolated‐word recognition task. The word recognition accuracy obtained was about 86.7%.

A proxy signature allows a designated person, called a proxy signer, to sign the message on behalf of the original signer. Proxy signatures are very useful tools when one needs to delegate his/her signing capability to other party. A number of proxy signature schemes have been proposed and succeeded for proxy delegations, but the schemes are in defective in proxy revocations. In this paper, we propose two proxy signature schemes based on RSA cryptosystems. The proposed first scheme does not consider proxy revocation mechanism; however, it will help us to compare our protocol with the existing RSA‐based schemes. The proposed second scheme provides an effective proxy revocation mechanism. The proposed schemes do not require any secure channel to proxy key delivery and support the necessary security requirements of proxy signature.

A computational model of the spatial‐frequency filtering processes at the level of 4Cβ layer of the visual striate cortex is being proposed. The model does not interfere with the filtering performed by the cortical receptive fields itself, and the focus of attention is restricted to the cortical input. The model is based on the literature data concerning the conformal mapping of the visual field representation at the primary visual cortex and uniformity of short‐range horizontal connections of cortical neurons. To test the model, the illusory figures were used as input stimuli, responses to which were computed and the output patterns constructed. The psychophysical experiments employing the same illusory figures were performed. A rather good correspondence between the model predictions and the experimental measurements of perceived size distortions was observed. In practice, the neurophysiological model provides a simplified and relatively fast algorithm of evaluation of distortions caused by filtering.

The undeniable signature, introduced by Chaum et al. in 1989, provides a nice property that the signer has an additional control over who will benefit from being convinced by the signature. However, a conspicuous drawback of undeniable signature is that the signer may be unavailable or refuse to cooperate. Chaum in 1994 proposed a designated confirmer signature scheme to protect the recipient's right. There exists a confirmer, who can always help the recipient prove the validity of the signature to others. Unfortunately, Chaum's paper did not consider that a malicious confirmer proves the validity of the signature to any persons as his will or even leaks the sensitive information to the signer's enemies. This paper proposes a new signature scheme called proxy confirmation signature where the proxy confirmer can only acquire a temporary proxy confirmation capability instead of a perpetual one from the signer. That is, the signer not only can delegate the confirmation capability to the proxy confirmer, but also can revoke the proxy confirmer's capability for avoiding the abuse. Moreover, our scheme also provides a technique to properly restrict the proxy confirmer to convincing only some specified verifiers that the signature is valid.

The contribution of this paper is a new version of the escape time algorithm adapted to synthesize fractal images, identified with attractors of iterated function systems (IFS). The proposed synthesis algorithm is based on the use of shift dynamics, associated with one or another IFS. The novelty of the algorithm is grounded on two factors. Firstly, the strategy for the separation of extended domains of the inverse affine transformations, specified by IFS, is developed. Secondly, the variable escape time for different points of a synthesized fractal image (IFS attractor) is proposed and explored. Experimental results show that the above two factors ensure uniform rendering of image points (pixels) in colour.

A novel approach to outlier detection on the ground of the properties of distribution of distances between multidimensional points is presented. The basic idea is to evaluate the outlier factor for each data point. The factor is used to rank the dataset objects regarding their degree of being an outlier. Selecting the points with the minimal factor values can then identify outliers. The main advantages of the approach are: (1) no parameter choice in outlier detection is necessary; (2) detection is not dependent on clustering algorithms.

A temporal logic of belief and actions (TLBA) is considered. The TLBA allows us to express informational and dynamic properties of computational agents. The considered fragment of TLBA allows one: (1) to present a deduction‐based structured decision procedure; (2) to separate a decision procedure for so‐called induction‐free formulas and (3) to use only logical axioms for such formulas. The main new technical tool of the presented decision procedure is separation rules which incorporate traditional rules for the temporal operator “next”, belief modalities and action constants.

The present paper describes the development and the performance of parallel FEM software for solving various CFD problems. Domain decomposition strategy and parallel iterative GMRES solver have been adapted to the universal space‐time FEM code FEMTOOL, which allows implementation of any partial differential equation with minor expenses. The developed data structures, the static load balancing and the inter‐processor communication algorithms have been particularly suited for homogeneous distributed memory PC clusters. The universality of the considered parallel algorithms has been validated solving applications described by the Poisson equation, by the convective transport equation and by the Navier–Stokes equations. Three typical benchmark problems have been solved in order to perform the efficiency study. The performance of parallel computations, the speed‐up and the efficiency have been measured on three BEOWULF PC clusters as well as on the cluster of IBM RISC workstations and on the IBM SP2 supercomputer.