Informatica

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.

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.

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.

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.

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 paper deals with the use of dynamic programming for word endpoint detection in isolated word recognition. Endpoint detection is based on likelihood maximization. Expectation maximization approach is used to deal with the problem of unknown parameters. Speech signal and background noise energy is used as features for making decision. Performance of the proposed approach was evaluated using isolated Lithuanian words speech corpus.

The quadratic assignment problem (QAP) is one of the well‐known combinatorial optimization problems and is known for its various applications. In this paper, we propose a modified simulated annealing algorithm for the QAP – M‐SA‐QAP. The novelty of the proposed algorithm is an advanced formula of calculation of the initial and final temperatures, as well as an original cooling schedule with oscillation, i.e., periodical decreasing and increasing of the temperature. In addition, in order to improve the results obtained, the simulated annealing algorithm is combined with a tabu search approach based algorithm. We tested our algorithm on a number of instances from the library of the QAP instances – QAPLIB. The results obtained from the experiments show that the proposed algorithm appears to be superior to earlier versions of the simulated annealing for the QAP. The power of M‐SA‐QAP is also corroborated by the fact that the new best known solution was found for the one of the largest QAP instances – THO150.

The paper presents the comparison of fuzzy conclusions derived from the use of t‐norms with the fuzzy conclusions derived from the use of H‐norm. The idea was to examine the application of H‐logical norm to fuzzy reasoning, which is not monotonious while it is known that t‐norms used in fuzzy reasoning have the characteristic of monotonicity. The comparison of fuzzy conclusions was performed by the use of coherence measure. The research was carried out on a relatively small number of examples (nine) and it was shown that the fuzzy conclusions derived from the use of H‐norm were the closest to the fuzzy conclusions derived from TL‐norm.

Cataract is very frequent disease of human eye and the diagnosis of this disease is not difficult. However, it is important to describe it quantitatively, but it is difficult using only the slit lamp. Ultrasound examinations are widely used in ophthalmology. Piezoelectric crystals generate ultrasound waves of 5–50 MHz. Short pulses of 2 to 3 cycles are sent from transducer into the eye. These pulses go through the tissues of the eye with the speed that is inversely proportional to the density and elasticity of the eye. Acoustic parameters of biologic tissues are described by velocity and attenuation coefficient. It is known that in soft tissues the attenuation coefficient is approximately proportional to the frequency – high frequency components of echoes are attenuated more than the lower frequency components. Results of ultrasound attenuation characteristics of human nuclear cataract are presented. It was shown that ultrasound attenuation of nuclear cataract could be used as “second opinion” for physicians decision support.

The paper deals with the analysis of the two survival models of the accelerated failure‐time using two‐parametrical log‐logistic and Weibull distributions, and survival models using conditional generalized Weibull, log‐logistic, and Smith and Bain distributions. The observed survival (number of deaths during the 30‐year follow‐up period among the study cohort) and the survival predicted by regression models (predicted number of deaths for the same period of time) were compared. Data on deaths occurring in random sample of men were obtained from the death register of the city of Kaunas. The best agreement between the predicted and observed survival was obtained with one of the modified Smith and Bain models.