Informatica

This research work is aimed at the development of data analysis strategy in a complex, multidimensional, and dynamic domain. Our universe of discourse is concerned with the data mining techniques of data warehouses revealing the importance of multivariate structures of social‐economic data which influence criminality. Distinct tasks require different data structures and various data mining exercises in data warehouses. The proposed problem solution strategy allows choosing an appropriate method in recognition processes. The ensembles of diverse and accurate classifiers are constructed on the base of multidimensional classification and clusterisation methods. Factor analysis is introduced into data mining process for revealing influencing impacts of factors. The temporal nature and multidimensionality of the target object is revealed in dynamic model using multidimension regression estimates. The paper describes the strategy of integrating the methods of multiple statistical analysis in cases, where a great set of variables is observed in short time period. The demonstration of the data analysis strategy is performed using real social and economic development of data warehouses in different regions of Lithuania.

The main purpose of the paper is to compare ontology‐based reuse techniques in domain engineering and enterprise engineering. It discusses attempts to combine classical domain engineering techniques with ontology‐based techniques as well as the attempts to incorporate ontologies in enterprise engineering process and demonstrates that, on the one hand, both approaches still are not mature enough to solve practical reuse problems and, on the other hand, both propose ideas that can be used to develop more mature approach. The main contribution of the paper is the detail description of the problems of ontology‐based reuse of enterprise engineering assets.

An authenticated encryption allows the designated recipient to verify the authenticity while recovering the message. To protect the recipient's benefit in case of a later dispute, a convertible authenticated encryption scheme allows the recipient to convert the authenticated encryption into an ordinary signature so that it becomes a publicly verifiable. This paper shows a universal forgery attack on Araki et al.'s convertible authenticated encryption scheme, and proposes a new convertible authenticated encryption scheme. Without using any conventional one‐way function, the proposed scheme simplifies its security assumption on only a public hard problem – the discrete logarithm problem.

In this paper, we shall propose a new method for the copyright protection of digital images. To embed the watermark, our new method partitions the original image into blocks and uses the PCA function to project these blocks onto a linear subspace. There is a watermark table, which is computed from projection points, kept in our new method. When extracting a watermark, our method projects the blocks of the modified image by using the PCA function. Both the newly projected points and the watermark table are used to reconstruct the watermark. In our experiments, we have tested our scheme to see how it works on original images modified by JPEG lossy compression, blurring, cropping, rotating and sharpening, and the experimental results show that our method is very robust and indeed workable.

The discrete Fourier transform (DFT) is used for determining the coefficients of a transfer function for n‐order singular linear systems, Ex⁽ⁿ⁾=Σi=1ⁿAix⁽ⁿ⁻¹⁾+Bu, where E may be singular. The algorithm is straight forward and easily can be implemented. Three step‐by‐step examples illustrating the application of the algorithm are presented.

The results of experimental testing of balanced random interval arithmetic with typical mathematical test functions and practical problem are presented and discussed. The possibility of evaluation ranges of functions using balanced random interval arithmetic is investigated. The influence of the predefined probabilities of standard and inner interval operations to the ranges of functions is experimentally investigated.

In 2001, Hsu et al. proposed a non‐repudiable threshold proxy signature with known signers. In their scheme, the proxy group cannot deny having signed the proxy signature if they did. However, Hsu et al.'s scheme is vulnerable to some attacks. A malicious original signer or malicious proxy signer can impersonate some other proxy signers to generate proxy signatures. In this article, we shall present our cryptanalysis of the Hsu et al.'s scheme. After that, we shall propose a new threshold proxy signature that can overcome the weaknesses.

The study of 3‐D indoor accurate scenery modeling is an active research area. The produced model can be used in a number of virtual reality applications, in digital documentation of monuments and sites, and so on. Digital photogrammetry and CAD technology have to play a vital role in this field. Photogrammetry's contribution is mainly on data acquisition from imagery, whilst the necessary image knowledge is derived from geometry and topology of image contents. While the first is traditionally used, the second one only lately is been tackled.

This paper deals with the absolute stability of single‐input single‐output time‐delay systems with, in general, a finite number of non commensurate constant internal point delays for any nonlinearity satisfying a time positivity inequality related to the first and third quadrants. The results are obtained based on Lyapunov's stability analysis via appropriate Lyapunov's functions and the related stability study is performed to obtain both delay independent and delay dependent results.

Recently iterative procedure for the restoration of speech signals when prosodic elements: stress and accent, of comparatively long duration are missing was developed. Alternatively, it could be cast in a signal generation framework. Basing on that view the paper presents the efficient implementation scheme for the restoration of voiced speech signals. It enjoys parallel order of multirate processing utilizing interpolation and decimation filters parameterized by specific to problem coefficients. Presented simulation results confirm the feasibility of developed implementation.