Informatica

Regarding the complexity of actual software systems, including web portals, it is becoming more and more difficult to develop software systems such that their real usage will satisfy their intended usage. To tackle this problem, we can compare the a priori assumptions about how the system should be used with the actual user behavior in order to decide how the system could be improved. For this aim, we propose to employ the same formalism to express the intended usage, the web portal model and the real usage extracted from system usage traces by data mining algorithms. Inspired from BioCham, we propose to use temporal logic and Kripke structure as such a common formalism.

This paper aims to extend fuzzy MULTIMOORA with linguistic reasoning and group decision-making (MULTIMOORA-FG). The new method consists of the three parts, namely the fuzzy Ratio System, the fuzzy Utopian Reference Point, and the fuzzy Full Multiplicative Form offering a robust comparison of alternatives against multiple objectives. In addition, MULTIMOORA-FG is designed to deal with triangular fuzzy numbers which, in turn, can resemble linguistic variables. MULTIMOORA-FG is a proper instrument for linguistic reasoning under fuzzy environment. In our study an application of personnel selection illustrates the group decision-making procedure according to MULTIMOORA-FG. Given the uncertainties peculiar of personnel selection, the application of multi-objective decision making (MODM) is required in this area. Fuzzy MULTIMOORA enables to aggregate subjective assessments of the decision-makers and thus offer an opportunity to perform a more robust personnel selection. The committee decided to consider eight qualitative characteristics expressed in linguistic variables. A numerical example exhibited possibilities for improvement of human resources management or any other business decision-making by applying MULTIMOORA-FG.

User anonymity is very important security technique in distributed computing environments that an illegal entity cannot determine any information concerning the user's identity. In 2006, Kumar–Rajendra proposed a Secure Identification and Key agreement protocol with user Anonymity (SIKA). This paper demonstrates the vulnerability of the SIKA protocol and then presents an improvement to repair the security flaws of the SIKA protocol.

In some cases of using multi-criteria decision making methods for solving real-world problems ratings of alternatives cannot be determined precisely, and that is why they are expressed in the form of intervals. Therefore, the aim of this paper is to extend the MOORA method for solving decision making problems with interval data. By extending the ratio system part of MOORA method, an algorithm to determine the most preferable alternative among all possible alternatives, when performance ratings are given as intervals, is presented. Finally, an example is shown to highlight the proposed procedure, at the end of this paper.

In this paper, a piecewise uniform quantizer for input samples with discrete amplitudes for Laplacian source is designed and analyzed, and its forward adaptation is done. This type of quantizers is very often used in practice for the purpose of compression and coding of already quantized signals. It is shown that the design and the adaptation of quantizers for discrete input samples are different from the design and the adaptation of quantizers for continual input samples. A weighting function for PSQNR (peak signal-to-quantization noise ratio), which is obtained based on probability density function of variance of standard test images is introduced. Experiments are done, applying these quantizers for compression of grayscale images. Experimental results are very well matched to the theoretical results, proving the theory. Adaptive piecewise uniform quantizer designed for discrete input samples gives for 9 to 20 dB higher PSQNR compared to the fixed piecewise uniform quantizer designed for discrete input samples. Also it is shown that the adaptive piecewise uniform quantizer designed for discrete input samples gives higher PSQNR for 1.46 to 3.45 dB compared the adaptive piecewise uniform quantizer designed for continual input samples, which proves that the discrete model is more appropriate for image quantization than continual model.

In this paper the gaze tracking system based on the adaptively changing threshold value of the gray level, which automatically detects the pupil position in two dimensional data is proposed. The system detects closed eye using normalized accumulative luminosity function. The detection of closed eye allows the confirmation of voluntary selected command in a more natural way. The presented technique allows recalibration without intervention or help of other assistive persons. Natural head motion is evaluated, employing signals, generated by orientation sensor. Within two experiments, the proposed system is tested at different behavior modes in respect of speed and accuracy of the system.

A simple Stock Exchange Game Model (SEGM) was introduced in Mockus (2003), to simulate the behavior of several stockholders using fixed buying-selling margins at fixed bank yield.

In this paper a forward–backward basis function approach for instantaneous frequency estimation of the frequency-modulated signal in noisy environment is presented. At first, a forward–backward prediction approach is applied for least squares estimation of time-varying autoregressive parameters. A time-varying parameters are expressed as a summation of constants multiplied by basis functions. Then, the time-varying frequencies are extracted from the time-varying autoregressive parameters by calculating the angles of the estimation error filter polynomial roots. The experimental results are presented, which shows the superiority of the proposed method against the covariance (forward prediction) approach.

This paper considers a new method for reconstructing deliberately-corrupted pixels in raster images. Firstly, a faster approach for reconstructing corrupted pixels is proposed by applying a processing-circle instead of a processing-square. It is shown that the obtained quality of the reconstructed image is no worse because of this. The quality of the reconstruction is further improved by controlling the pixel corrupting process within the input image. It is shown that a combination of the processing-circle approach and data-dependent corruption reduces the reconstruction time, and the mistakes of the reconstructed pixels.

Key-insulated cryptography is an important technique to protect private keys in identity-based (IB) cryptosytems. Despite the flurry of recent results on IB key-insulated encryption (IBKIE) and signature (IBKIS), a problem regarding the security and efficiency of practicing IBKIE and IBKIS as a joint IB key-insulated signature/encryption scheme with a common set of parameters and keys remains open. To deal with the above question, we propose an identity-based key-insulated signcryption (IBKISC) scheme. Compared with the Sign-then-Encrypt (StE) and Encrypt-then-Sign (EtS) using IBKIE and IBKIS in the standard model, our proposed IBKISC scheme is the fastest with the shortest ciphertext size.