Informatica

This paper presents a new in‐place pseudo linear radix sorting algorithm. The proposed algorithm, called MSL (Map Shuffle Loop) is an improvement over ARL (Maus, 2002). The ARL algorithm uses an in‐place permutation loop of linear complexity in terms of input size. MSL uses a faster permutation loop searching for the next element to permute group by group, instead of element by element. The algorithm and its runtime behavior are discussed in detail. The performance of MSL is compared with quicksort and the fastest variant of radix sorting algorithms, which is the Least Significant Digit (LSD) radix sorting algorithm (Sedgewick, 2003).

The article presents a limited‐vocabulary speaker independent continuous Estonian speech recognition system based on hidden Markov models. The system is trained using an annotated Estonian speech database of 60 speakers, approximately 4 hours in duration. Words are modelled using clustered triphones with multiple Gaussian mixture components. The system is evaluated using a number recognition task and a simple medium‐vocabulary recognition task. The system performance is explored by employing acoustic models of increasing complexity. The number recognizer achieves an accuracy of 97%. The medium‐vocabulary system recognizes 82.9% words correctly if operating in real time. The correctness increases to 90.6% if real‐time requirement is discarded.

The problem of post‐processing of a classified image is addressed from the point of view of the Dempster–Shafer theory of evidence. Each neighbour of a pixel being analyzed is considered as an item of evidence supporting particular hypotheses regarding the class label of that pixel. The strength of support is defined as a function of the degree of uncertainty in class label of the neighbour, and the distance between the neighbour and the pixel being considered. A post‐processing window defines the neighbours. Basic belief masses are obtained for each of the neighbours and aggregated according to the rule of orthogonal sum. The final label of the pixel is chosen according to the maximum of the belief function.

In this paper a useful educational tool is presented for minimizing low order Boolean expressions. The algorithm follows the Karnaugh map looping approach and provides optimal results. For the implementation, C++ was used on the CodeWarrior for Palm Operating System environment. In order to make the overall implementation efficient, the object oriented approach was used. Two step‐by‐step examples are presented to illustrate the efficiency of the proposed algorithm. The proposed application can be used by students and professors in the fields of electrical and computer engineering and computer science.

This paper develops a representation of multi‐model based controllers by using artificial intelligence typical structures. These structures will be neural networks, genetic algorithms and fuzzy logic. The interpretation of multimodel controllers in an artificial intelligence frame will allow the application of each specific technique to the design of improved multimodel based controllers. The obtained artificial intelligence based multimodel controllers are compared with classical single model based ones. It is shown through simulation examples that a transient response improvement can be achieved by using multiestimation based techniques. Furthermore, a method for synthesizing multimodel based neural network controllers from already designed single model based ones is presented. The proposed methodology allows to extend the existing single model based neural controllers to multimodel based ones, extending the applicability of this kind of techniques to a more general type of controllers. Also, some applications of genetic algorithms and fuzzy logic to multimodel controller design are proposed. Thus, the mutation operation from genetic algorithms inspires a robustness test which consists of a random modification of the estimates which is used to select the estimates leading to the better identification performance towards parameterizing online the adaptive controller. Such a test is useful for plants operating in a noisy environment. The proposed robustness test improves the selection of the plant model used to parameterize the adaptive controller in comparison to classical multimodel schemes where the controller parameterization choice is basically taken based on the identification accuracy of each model. Moreover, the fuzzy logic approach suggests new ideas to the design of multiestimation structures which can be applied to a broad variety of adaptive controllers such as robotic manipulator controller design.

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.

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.

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.

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.

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.